How to estimate the age of an oak tree


Tree Age Calculator - How Old Is a Tree?

Created by Mehjabin Abdurrazaque

Reviewed by Wojciech Sas, PhD and Rijk de Wet

Last updated: Sep 28, 2022

Table of contents:
  • How to calculate the age of a tree?
  • How to use tree age calculator?
  • Tree growth factor chart — the smaller, the faster!
  • FAQ

The tree age calculator guides you on how to calculate the age of a tree to understand its ecological and economical benefits, as you can learn at the tree value calculator. Our tool also tells you how much a tree grows in diameter or circumference in the given time so that you can design your yard suitably.

We also try to answer some interesting questions like:

  • Do trees die of old age?
  • How to tell how old a tree is by counting its rings?

And, don't forget to check our tree growth factor chart to find the fast-growing trees in your neighborhood!

How to calculate the age of a tree?

The formula for calculating a tree's age is

age=gf⋅dbh\text{age} = \text{gf}\cdot \text{dbh}age=gf⋅dbh

Where:

  • age\text{age}age — The tree's age in years;
  • gf\text{gf}gf — The tree growth factor; and
  • dbh\text{dbh}dbh — The diameter at breast height in inches.

Follow these steps to find your tree's age using this formula:

  1. Measure the circumference at breast height (cbh) of the tree trunk using a measuring tape at 4.5 feet (1.3 meters) above the ground.
  2. Divide the circumference cbh by pi (≈3.14) to obtain its diameter at breast height (dbh\text{dbh}dbh).
  3. Convert dbh\text{dbh}dbh to inches.
  4. Multiply the diameter in inches with the tree species' growth factor.

Growth factor of a tree
To determine a tree species' growth factor, scientists first estimate the actual age of trees of that species by counting their growth rings. Then, they divide the trees' diameters at breast height (we met this quantity at our tree diameter calculator) with their actual ages to obtain the tree species' growth factor.

How to use tree age calculator?

It's very simple: select the type of tree and input the tree's circumference or diameter. 😎✨

Suppose you want to know the age of your red maple with a circumference of 6 feet and 3 inches (= 2 feet in diameter). To determine your tree's age using our tool, you'd follow these steps:

  1. Scroll down the tree species' drop-down list and select Red maple.
  2. To calculate your tree's age from its circumference:
    • Choose the unit for circumference at breast height (cbh\text{cbh}cbh) from the drop-down list beside its input box. For your red maple, the unit is feet/inches. Then enter the circumference of 6 feet and 3 inches (if you are not familiar with this way to express length, visit the feet and inches calculator).
    • Enter the tree's circumference in the input box — 666 in the box to the left of ft\text{ft}ft and 333 in the box to the left of in\text{in}in.

Ta-da! The calculator shows your tree's diameter at breast height (dbh\text{dbh}dbh) is 61 cm61\ \text{cm}61 cm (you can convert the length to obtain the diameter in feet or feet and inches) and its age 107 years107\ \text{years}107 years! It's a centenarian!

If you want to tell the tree's age from its diameter:

  • Choose the unit for diameter at breast height from the drop-down list beside its input box — feet ($$\text{ft}$$).
  • Enter your tree's diameter in the input box — 222.

🙋 If you can't find your tree in the list, enter your tree's growth factor in the input box for Growth factor. Most tree species have growth factors of 3, 4, or 5.

Did you know that you can roughly estimate your tree's birthday using our date calculator! Just enter your tree's age in days and today's date in our tool, and you can obtain a date close to your tree's actual birthday.

Tree growth factor chart — the smaller, the faster!

You can use our tree growth factor not only to calculate your tree's age but also to learn which trees grow faster than your tree. The rule is: The smaller the tree growth factor, the faster the tree grows.

While you are here, check out our tree spacing calculator. It will help you determine the correct distance for planting different types of trees.

The tree growth factor chart for many different species of tree.

Tree species

Growth factor

American beech

6

American elm

4

American sycamore

4

Austrian pine

4.5

Basswood

3

Black cherry

5

Black maple

5

Black walnut

4.5

Black willow

2

Box elder

3

Bradford pear

3

Common horse chestnut

8

Colorado blue spruce

4.5

Cottonwood

2

Dogwood

7

Douglas fir

5

European beech

4

European white birch

5

Green ash

4

Honey locust

3

Ironwood

7

Kentucky coffee tree

3

Littleleaf linden

3

Northern red oak

4

Norway maple

4. 5

Norway spruce

5

Pin oak

3

Quaking aspen

2

Redbud

7

Red maple

4.5

Red pine (Norway pine)

5.5

River birch

3.5

Scarlet oak

4

Scotch pine

3.5

Shagbark hickory

7.5

Shingle oak

6

Shumard oak

3

Silver maple

3

Sugar maple

5.5

Sweetgum

4

Tulip tree

3

White ash

5

White fir

7. 5

White oak

5

White pine

5

Yellow buckeye

5

FAQ

Do trees die of old age?

As a tree ages, its respiring tissue increases, but the photosynthetic area (leaf surface area) remains somewhat constant. Consequently, an older tree allocates more carbohydrates for life-sustaining respiration and less carbohydrate for root and stem elongation and repair, which initiates its senescence (physiological deterioration) phase. The tree becomes more vulnerable to diseases and other natural enemies and eventually becomes a snag.

How can I identify the fast-growing trees near me?

It's easier to find out which trees grow faster than others using the tree growth factor chart. The smaller the growth factor, the faster the tree grows!

How do I calculate an oak tree's age by diameter?

To determine an oak tree's age by diameter:

  • Convert the diameter to inches.
  • Multiply the diameter with the tree species' growth factor.
  • The product is the tree's age in years!

For example, the age of your pin oak tree with a diameter of 3 ft at breast height (dbh) is 3 (the growth factor) times 39 (dbh in inches) = 117 years!

How do I count tree rings to estimate its age?

Each dark ring of the tree trunk represents a cycle of seasons, or one year. So, the total number of dark rings tells us the age of the tree in years. Count from the innermost dark ring to the outermost.

Mehjabin Abdurrazaque

Tree species

Growth factor

Circumference at breast height

Diameter at breast height

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How Old Do Oak Trees Get? (And How Do You Determine the Age?)

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This question is a great one! You might be asking this question because you have an oak in your yard or elsewhere on your property that has been there longer than anyone can remember, and you would love to know its age.

Or you have heard tales of how old some southern USA oak trees have gotten. Either way, it is a worthy question to ask and a fun project if you have a few minutes, a long tape measure, and a calculator.

So the answer to this question about how old oak trees get will be interesting but might not help you as much as the answer to the question: how can you tell how old an oak tree is? This calculation is essential if you are trying to calculate an estimated age of an oak tree on your property.

Well, great news! This article will answer both of those questions. You just might have to do a little math along the way.

How Old?

The answer to how old oak trees can get may surprise you. Scientists have estimated that several famous oak trees are over 1,000 years old!

The legendary Angel Oak near Johns Island, South Carolina, is estimated to be nearly 1,500 years old. Check out this article for some of those other famous oak trees across the southern USA.

It is remarkable to consider how many generations of your ancestors lived and died while those trees have been alive. They are indeed a gift to be treasured.

Many are breathtakingly large with complex systems of branches and trees. Some of the most iconic are decorated by Spanish moss.

Those trees that live over 1,000 years tend to be remarkable and exceptional indeed. Scientists say that 1,000 years is the topmost lifespan for an oak tree.

There are a host of factors that can cause trees to die out much younger than that age as well, including what type of oak tree it is and where it is growing. More details on that below.

But just so you know, oak tree ages are estimated, because unless you were there when it first sprouted from an acorn, the most reliable method for determining its age is counting its rings.

The only problem is that you can’t reliably do so until after the tree has died. Oak trees produce a ring for every year it lives. But you certainly don’t want to cut down a tree to see how long it has been alive!

It is possible to take a core from a live tree with a borer to determine its age, but to do so can introduce damage or disease to the tree if the procedure is not done correctly. So another method should be used to determine how old it is.

Calculate the Age of Your Oak Tree

These four steps will guide you on how to calculate a rough estimate of the age of your tree without injuring it in any way.

  1. Measure its circumference. Use a measuring tape. Pick a spot that is approximately 4.5 feet from the ground to measure. This spot is a standard measurement spot for arborists. Your results will be accurate if you measure at this height.
  2. Convert your measurement into inches. So, multiply every foot by 12 inches and then add the remaining inches for your total number of inches.
  3. Calculate the diameter of your tree. Divide the number of inches you determined to be the diameter of your tree and divide by 3.14 (that wonder constant people call pi). This number will be the diameter of your tree.
  4. Multiply the diameter by the growth factor for your species of oak. This calculation is essential to get correct because of the variety of growth rates for different trees. See the growth rates noted below.

Species Tree Growth Factor

  • White Oak 5
  • Red Oak 4
  • Pin Oak 3

If you don’t know the species of your tree, you can get an estimate by multiplying the diameter by 3, 4, and 5.

You can reasonably guess that the age of your oak will fall within that range. In fact, many people advise the best estimate is to multiply by 4 — right in the middle of those numbers.

If you want to know exactly what kind of tree you have, you will need to look closely at the leaf types for the best opportunity to identify which oak you have. You might also check this list of common oak types, which includes the following.

Types of White Oak Trees

  • Chinkapin
  • Post Oak
  • Bur Oak
  • White Oak

Types of Red Oak Trees

  • Willow Oak
  • Black Oak
  • Japanese Evergreen Oak
  • Water Oak
  • Pin Oak

One Note About Calculating Age

The truth is that a growth factor assumes even growth year after year, but as is widely known, life is usually more about hills and valleys than steady, consistent living.

According to rainfall and sun from year to year and location of the tree, there can be a wide variety of growth from year to year.

Trees in more populated areas grow differently than those in the woodland areas. Urban dwelling trees grow more slowly because of the stress that comes with living in the city: traffic, heat from the concrete, and stress on its roots.

So tree growth rates will need to be adjusted slightly because they grow slower in urban areas. Many suggest that there is as much as a 25% difference in urban growth rates over time.

Unfortunately, growth in an urban area can also shorten the life of a tree. Some calculate they may live for half the number of years as a tree might in a field free from competition.

Fun Facts About Oaks

  • Oakwood is so dense and heavy that it was used to make battleships. The USS Constitution was called “Old Ironsides” in the War of 1812, not because it was made of iron. In fact, it was a live oak hull so dense that cannonballs fired from British warships bounced off of it!
  • Acorns are produced by the thousands every fall by mature oak trees. Acorns are feasted on by squirrels and also by pigs, bears, and deer.
  • The name “live oak” was attributed to oak trees because oaks are green every day of the year.
  • Oaks provide homes to birds, squirrels, and Spanish moss.
  • A mature oak can drink more than 50 gallons of water per day through its deep roots.
  • Live oaks can stand up to 100 feet tall.
  • The crowns of the most enormous live oaks reach diameters of 150 feet across.

History Fun

  • The Friendship Oak of Long Beach, Mississippi, is over 500 years old and has survived numerous hurricanes over the years.
  • The Seven Sisters Oak of Louisburg, Louisiana, is another oak estimate to be more than 1,000 years old. How big is its circumference? Over 37 feet!
  • The Cellon Oak of Alachua, Florida, is so big that it can be seen from space.
  • The Dueling Oaks of New Orleans, Louisiana, were famous for the duels that took place under them. Just as dueling has become a thing of the past, one of these renowned oak trees was toppled during a hurricane, but the other remains and is growing stronger every year.

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How to determine the age of an oak tree

How to determine the age of an oak tree is a question that sooner or later gardeners or just passers-by face when a huge and powerful representative of this type of tree has fallen before their eyes. And since oaks are long-lived and have a fairly strong trunk and a luxurious crown, it’s not so easy to answer the question about age. For all the time of the existence of mankind, there are only a few ways to find out this information. Let's consider them in more detail.

Since childhood, we were told that the age of any tree can be determined by counting the annual rings on the cut of the trunk. Yes, this is true, but the method, firstly, is too radical, because it is unlikely that someone will cut down an oak tree just to find out its age. There are other, less radical methods that can provide information of interest to us. These include:

  • whorls count;
  • stem diameter measurement;
  • Pressler drill application.

But none of the methods described above will help to determine the age of a tree with an accuracy of 99%, why we will consider this further.

Therefore, if the question is quite fundamental, then in addition to the methods described, it is necessary to resort to searching for information about the oak you are interested in. It is collected in several ways. The first is a survey. It is necessary to interview local residents, for sure someone has information about when the tree was planted or maybe knows for sure that it grew in this place when his grandmother was a child (such information gives certain ideas about age). The second way is to study documents and photographs. These can be newspaper archives, home photo albums, and if the tree grows in a park area, then you can try to find information from the city authorities. After all, most likely the alleys and parks were planted during subbotniks or were timed to coincide with some memorable events. It happens that the tree of interest grows on the territory of someone's former estate or church, then it is worth looking for information about the owners of the estate or studying historical data about the church and talking with the priest. Sometimes the search for the necessary information allows you to get the most reliable data, and besides, to learn a lot of new things, and not only about the tree.

But if it was not possible to determine the age of the oak by information, then it is necessary to proceed to the biological one.

And so, counting whorls. What it is. Simply put, it is necessary to count the number of tiers of tree branches that are located around the trunk. Every year the tree forms a new ring of branches. Having counted the whorls, it is necessary to add the number three to their number, since the oak only in the third year begins to form branches that form the annual circle. The added numbers are the age of the tree. But, since the oak belongs to the centenarians, and today individual specimens are known that are already more than a thousand years old, this method of determining the age of it is suitable only for young trees. This is due to the fact that after thirty years of life, the lower branches of oaks begin to die off and fall off, and its size can reach fifty meters in height, so it is almost impossible to correctly calculate whorls.

The next way to determine the age of an oak tree is to measure the diameter of its trunk. This will require a special device - a forest measuring fork, but you can also use a regular tailor centimeter for measurement. Measurements are taken at a distance of one meter thirty centimeters from the ground. Having measured the circumference of a tree, simple mathematical calculations determine the diameter through the circumference and the number pi. Next, you need to know the data on the average annual growth. Oak grows on average by forty-four millimeters. To calculate the age, the diameter is divided by a factor of 44. This is how we find out how old the tree is. But it should be noted that melon calculations have a mathematical error of five to fifteen percent. Since it is impossible to give exact figures on annual growth. These natural processes depend on the environment and conditions in which the tree grows.

The indicated methods for determining the age of a tree are quite loyal and allow you to determine the age without cutting down the trunk.

Less loyal, but still not so cardinal, is the use of a Pressler drill. With it, you can take a sample of wood from the bark to the core. Rings are counted on the obtained sample. Now a few words and technique. The drill must be suitable in size, its length is seventy-five percent of the diameter of the tree. Wood sampling is carried out at a distance of one meter thirty centimeters from the ground. The drill must be screwed into the barrel with translational movements. After receiving the wood, it is inspected for growth rings. Although this method harms the tree trunk, it allows you to more accurately determine the age without destroying it. In addition, oak has a good ability to recover. The place where the wood sample was taken will soon be overgrown.

And of course, a way to count tree rings on the trunk. It is only suitable for determining the age of already cut trees. But it also does not give one hundred percent confidence in the correct calculation. Since, due to certain circumstances (weather conditions, tree diseases, etc. ), the tree may not form a ring in one year. Therefore, the calculation of age by rings is also not accurate. But in general, one ring on the trunk indicates one year of life of this tree.

Oak age by trunk diameter table

Oak measurements:
• total height – 26.9 m, trunk height to the first branches 3 m. 20 cm, average crown diameter – 13.5 m;
• dry branches in the crown 15%;
• There are child trees.
Next, we directly moved on to measuring the girth of the oak trunk at different heights from the ground. This, to a much greater extent, can help us in determining the exact age of the oak.
And this is what we got:
• at a height of 1 m. 50 cm from the ground: girth - 3 m. 38 cm, diameter - 109see
• maximum dimensions (1 m 30 cm from the ground): girth - 4 m. 22 cm, diameter - 134 cm;
• at ground level (excluding roots): girth - 4 m, diameter - 127 cm.

During the measurements of the trunk, we found six six frost cracks on the trunk. They also talk about the old age of the tree, but very roughly, because these are deep damage to the bark of the tree, which appear only at air temperatures below -30-40, which even happens rarely with us.
After studying the literature, we found about a dozen ways to determine the age of an oak tree.
Methods for determining the age of an oak:
Since only the most inaccurate methods for determining the age are available to us, we carried out all three methods of calculation:
• circumference at a height of 130 cm from the ground X coefficient 1 = 422 X 1= 422 years;
• circumference at a height of 150 cm from the ground X coefficient 0.8 = 338 X 0.8 = 270 years;
• proportion: if the circumference of a circle is 600 cm at a height of 130 cm from the ground, an oak tree is 500 years old, then 422 cm at the age of 351 years.
As a result, according to different calculation methods, we got the age of the tree from 270 to 422 years. Thus, the oak is about 300 years old!

How to determine the age of an oak, a question that gardeners or just passers-by face sooner or later, whose gaze was caught by a huge and powerful representative of this type of trees. And since oaks are long-lived and have a fairly strong trunk and a luxurious crown, it’s not so easy to answer the question about age. For all the time of the existence of mankind, there are only a few ways to find out this information. Let's consider them in more detail.

Since childhood, we were told that the age of any tree can be determined by counting the annual rings on the cut of the trunk. Yes, this is true, but the method, firstly, is too radical, because it is unlikely that someone will cut down an oak tree just to find out its age. There are other, less radical methods that can provide information of interest to us. These include:

  • whorl count;
  • stem diameter measurement;
  • Pressler drill application.

But with an accuracy of up to 99%, none of the methods described above will help to determine the age of a tree, why we will consider this further.

Therefore, if the question is quite fundamental, then in addition to the methods described, it is necessary to resort to searching for information about the oak you are interested in. It is collected in several ways. The first is a survey. It is necessary to interview local residents, for sure someone has information about when the tree was planted or maybe knows for sure that it grew in this place when his grandmother was a child (such information gives certain ideas about age). The second way is to study documents and photographs. These can be newspaper archives, home photo albums, and if the tree grows in a park area, then you can try to find information from the city authorities. After all, most likely the alleys and parks were planted during subbotniks or were timed to coincide with some memorable events. It happens that the tree of interest grows on the territory of someone's former estate or church, then it is worth looking for information about the owners of the estate or studying historical data about the church and talking with the priest. Sometimes the search for the necessary information allows you to get the most reliable data, and besides, to learn a lot of new things, and not only about the tree.

But if it was not possible to determine the age of the oak by information, then it is necessary to proceed to the biological one.

And so, counting whorls. What it is. Simply put, it is necessary to count the number of tiers of tree branches that are located around the trunk. Every year the tree forms a new ring of branches. Having counted the whorls, it is necessary to add the number three to their number, since the oak only in the third year begins to form branches that form the annual circle. The added numbers are the age of the tree. But, since the oak belongs to the centenarians, and today individual specimens are known that are already more than a thousand years old, this method of determining the age of it is suitable only for young trees. This is due to the fact that after thirty years of life, the lower branches of oaks begin to die off and fall off, and its size can reach fifty meters in height, so it is almost impossible to correctly calculate whorls.

The next way to determine the age of an oak tree is to measure the diameter of its trunk. This will require a special device - a forest measuring fork, but you can also use a regular tailor centimeter for measurement. Measurements are taken at a distance of one meter thirty centimeters from the ground. Having measured the circumference of a tree, simple mathematical calculations determine the diameter through the circumference and the number pi. Next, you need to know the data on the average annual growth. Oak grows on average by forty-four millimeters. To calculate the age, the diameter is divided by a factor of 44. This is how we find out how old the tree is. But it should be noted that melon calculations have a mathematical error of five to fifteen percent. Since it is impossible to give exact figures on annual growth. These natural processes depend on the environment and conditions in which the tree grows.

The indicated methods for determining the age of a tree are quite loyal and allow you to determine the age without cutting down the trunk.

Less loyal, but still not so cardinal, is the use of a Pressler drill. With it, you can take a sample of wood from the bark to the core. Rings are counted on the obtained sample. Now a few words and technique. The drill must be suitable in size, its length is seventy-five percent of the diameter of the tree. Wood sampling is carried out at a distance of one meter thirty centimeters from the ground. The drill must be screwed into the barrel with translational movements. After receiving the wood, it is inspected for growth rings. Although this method harms the tree trunk, it allows you to more accurately determine the age without destroying it. In addition, oak has a good ability to recover. The place where the wood sample was taken will soon be overgrown.

And of course, a way to count tree rings on the trunk. It is only suitable for determining the age of already cut trees. But it also does not give one hundred percent confidence in the correct calculation. Since, due to certain circumstances (weather conditions, tree diseases, etc. ), the tree may not form a ring in one year. Therefore, the calculation of age by rings is also not accurate. But in general, one ring on the trunk indicates one year of life of this tree.

As the tree grows, the thickness of its trunk increases every year due to the formation of a new annual ring. The average annual increase in thickness depends on the type of tree and local conditions.

To approximate the age of a tree, divide the trunk radius, measured at a height of about a meter (where it is already stabilized) , by the average thickness of its annual ring (see tables 1 and 2) . For example, the diameter of a birch trunk is 20 cm, which means its radius is 10 cm. A birch is a fast-growing tree with an increase of up to 2 mm per year. As a result, we get the age of the birch 10 / 0.2 = 50 years. For moderately growing and slow growing trees, you should also add the years for which they have grown to the level of the trunk measurement.


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