Tree Age Calculator: How Old Is My Tree?

Maintained by the Grant Brothers Tree Service arborist team. Last updated October 19, 2026.

To estimate a tree’s age, measure straight across the trunk at 4.5 feet (DBH) and pick the tree type. Yard and street trees grow faster than forest trees, so the calculator gives a range for each. For example, a red oak 20 inches across is about 25 to 50 years old in a yard, or about 65 to 105 years old in the woods.

Accurately estimate the age of trees using scientifically-backed methods. Our professional tree age calculator, also called a tree age estimator, finds a tree’s age by diameter. It helps arborists, foresters, homeowners, and tree enthusiasts find the approximate age of 42 kinds of trees from the trunk width (DBH). For yard and street trees, it uses a U.S. Forest Service study of city trees of known age. For forest trees, it uses the Purdue University growth factor chart. For a quick answer, see the tree age chart, or learn how to tell how old a tree is without a calculator.

Tree Age Chart by Diameter

How old is a tree that is 10, 20 or 30 inches across? This tree age chart gives the answer for 17 common trees. Measure straight across the trunk at 4.5 feet (DBH), then find your tree and the closest size (in = inches across). For example, a red oak 20 inches across is about 25 to 50 years old in a yard and 65 to 105 years old in the woods. Ages are in years.

Yard or street trees

Tree	10 in	20 in	30 in
Red oak	14 to 25	25 to 50	40 to 75
White oak	15 to 35	30 to 70	40 to 100
Pin oak	8 to 19	15 to 35	25 to 55
Live oak	11 to 12	20 to 25	35 to 45
Red maple	14 to 30	30 to 75	40 to 100 (rougher)
Sugar maple	15 to 30	30 to 50	40 to 70
Silver maple	13 to 35	25 to 65	35 to 95 (rougher)
Sweetgum	14 to 30	25 to 65	40 to 100
Eastern red cedar	17 to 40	35 to 80	50 to 115
White pine	12 to 30	35 to 80	50 to 120 (rougher)
Magnolia (estimate)	19 to 45	35 to 85	45 to 110
Tulip poplar (estimate)	15 to 25	30 to 45	45 to 70
Sycamore (estimate)	10 to 25	20 to 50	30 to 65 (rougher)
Black walnut (estimate)	25 to 35	45 to 70	70 to 100
American beech (estimate)	30 to 45	60 to 90	90 to 135
Willow (estimate)	15 to 25	30 to 45	45 to 70
Cottonwood or poplar (estimate)	10 to 15	20 to 30	30 to 45

Forest or crowded woods

Tree	10 in	20 in	30 in
Red oak	30 to 50	65 to 105	95 to 155
White oak	40 to 65	80 to 130	120 to 195
Pin oak	25 to 40	50 to 80	70 to 115
Live oak	20 to 35	40 to 65	60 to 100
Red maple	35 to 60	70 to 115	110 to 175
Sugar maple	40 to 65	80 to 130	120 to 195
Silver maple	25 to 40	50 to 80	70 to 115
Sweetgum	30 to 50	65 to 105	95 to 155
Eastern red cedar	45 to 70	90 to 145	130 to 215
White pine	40 to 65	80 to 130	120 to 195
Magnolia	50 to 80	95 to 155	145 to 235
Tulip poplar	25 to 40	50 to 80	70 to 115
Sycamore	30 to 50	65 to 105	95 to 155
Black walnut	35 to 60	70 to 115	110 to 175
American beech	50 to 80	95 to 155	145 to 235
Willow	25 to 40	50 to 80	70 to 115
Cottonwood or poplar	16 to 25	30 to 50	50 to 80

Yard trees grow faster than forest trees, so a yard tree is often younger than it looks. Yard ranges come from the U.S. Forest Service Urban Tree Database, which measured city trees of known age in Charlotte, NC (low end) and Queens, NY (high end). Live oak grows in the Southeast, so its yard range comes from Orlando, FL and Charleston, SC. Trees marked “estimate” were not measured in those cities, so their yard range uses a close relative or the Purdue University rule of thumb. The white oak, pin oak, eastern red cedar and white pine were measured in only one city, so one end of their yard range is estimated. “Rougher” means the trunk is bigger than the biggest tree the study measured. Forest ranges use trunk width times the tree’s growth factor. For any other size or tree, use the calculator above.

How Old Is an Oak Tree With a 3, 4, 5 or 6 Foot Trunk?

An oak with a trunk 3 feet across is about 50 to 95 years old in a yard (red oak) and about 115 to 185 years old in the woods. An oak 6 feet across can be about 70 to 470 years old. It depends on the kind of oak and where it grew. Ages are in years.

Trunk across	Red oak	White oak	Live oak
3 feet (36 in)	50 to 95 115 to 185	50 to 120 145 to 235	40 to 55 70 to 115
4 feet (48 in)	65 to 125 (rougher)155 to 250	65 to 155 190 to 310	55 to 65 95 to 155
5 feet (60 in)	80 to 155 (rougher)190 to 310	85 to 195 (rougher)240 to 390	60 to 80 (rougher)120 to 195
6 feet (72 in)	100 to 185 (rougher)230 to 375	100 to 235 (rougher)290 to 470	70 to 95 (rougher)145 to 235

In each box, the top number is a yard or street tree and the bottom number (gray) is a tree in the woods. These trunks are bigger than most trees in the studies, so these ranges are rough. Only a ring count gives the exact age. Did you measure around the trunk? Divide by 3.14 first. A trunk 6 feet (72 inches) around is about 23 inches across.

Tree Age by Species

Each kind of tree grows at its own speed. Pick your tree in the calculator above, or read the short notes below. Each example is for a trunk 20 inches across.

Oak tree age

A red oak 20 inches across is about 25 to 50 years old in a yard and 65 to 105 in the woods (growth factor 4.0). A white oak grows slower: about 30 to 70 years in a yard and 80 to 130 in the woods (growth factor 5.0). A pin oak grows faster: about 15 to 35 years in a yard and 50 to 80 in the woods (growth factor 3.0). Set the calculator to red oak.

Live oak tree age

A live oak 20 inches across is about 20 to 25 years old in a yard and 40 to 65 in the woods (growth factor 2.5, an estimate). Live oaks grow in the Southeast, so the yard numbers come from live oaks measured in Orlando, FL and Charleston, SC. Set the calculator to live oak.

Maple tree age

A red maple 20 inches across is about 30 to 75 years old in a yard and 70 to 115 in the woods (growth factor 4.5). A sugar maple is about 30 to 50 in a yard and 80 to 130 in the woods (growth factor 5.0). A silver maple grows fast: about 25 to 65 in a yard and 50 to 80 in the woods (growth factor 3.0). Set the calculator to red maple.

Pine tree age

A white pine 20 inches across is about 35 to 80 years old in a yard and 80 to 130 in the woods (growth factor 5.0, an estimate). The calculator also has red pine and Scots pine. For a young pine, you can count the branch whorls. Set the calculator to white pine.

Cedar tree age

For a cedar tree age, pick Eastern Red Cedar (also called juniper) in the calculator. A cedar 20 inches across is about 35 to 80 years old in a yard and 90 to 145 in the woods (growth factor 5.5, an estimate). The yard numbers come from cedars measured in Charlotte, NC. Set the calculator to Eastern Red Cedar.

Magnolia tree age

A magnolia 20 inches across is about 35 to 85 years old in a yard and 95 to 155 in the woods (growth factor 6.0, an estimate). The yard range is an estimate from southern magnolias measured in Charlotte, NC. Set the calculator to magnolia.

Sycamore tree age

A sycamore 20 inches across is about 20 to 50 years old in a yard and 65 to 105 in the woods (growth factor 4.0, an estimate). The yard range is an estimate from London plane trees, a close relative, measured in Queens, NY. Set the calculator to sycamore.

Willow and cottonwood tree age

These trees grow fast. A willow 20 inches across is about 30 to 45 years old in a yard and 50 to 80 in the woods (growth factor 3.0, an estimate). A cottonwood is about 20 to 30 in a yard and 30 to 50 in the woods (growth factor 2.0). Both yard ranges are estimates. Set the calculator to willow.

Beech and walnut tree age

These trees grow slowly. An American beech 20 inches across is about 60 to 90 years old in a yard and 95 to 155 in the woods (growth factor 6.0, an estimate). A black walnut is about 45 to 70 in a yard and 70 to 115 in the woods (growth factor 4.5). Both yard ranges are estimates.

How to Tell How Old a Tree Is

There are 5 ways to tell how old a tree is. Counting the rings is the most exact. Measuring the trunk is the easiest way for a living tree.

Count the rings on a stump. A tree adds one growth ring each year, so a stump with 73 rings is about 73 years old. If you count the rings higher up the trunk, add the years the tree took to grow to that height. At 4.5 feet, that is usually 5 to 10 years. Some years make an extra ring or a ring that is hard to see, so a ring count is still an estimate.
Take a core sample. An arborist or forester can use an increment borer. This hand tool pulls out a thin core of wood, about the size of a pencil, so you can count the rings without cutting the tree down. It can leave a small wound in the tree.
Measure the trunk (the DBH method). Measure around the trunk at 4.5 feet and divide by 3.14 to get the diameter. Then use the calculator above, or multiply the diameter by the tree’s growth factor. For example, a red oak 94 inches around is about 30 inches across. In the woods, that is about 30 x 4.0 = 120 years. In a yard, it is about 40 to 75 years, because yard trees grow faster.
Count the branch whorls on a young pine. Pines, spruces and firs grow one ring of branches (a whorl) around the trunk each year. Count the whorls from the ground to the top. Include the stubs and knots where low branches fell off. Then add 2 to 4 years for the seedling years. This works best on trees up to about 15 years old.
Check the planting records. If you know when the tree was planted, add its age at planting. Most trees are 5 to 10 years old when they leave the nursery.

Tree age from ring width

Know the width of the rings instead of the count? Divide the trunk’s radius (from the center to the inside of the bark) by the average ring width. For example, a radius of 13.5 inches with rings 3/4 inch wide gives 13.5 / 0.75 = 18 rings. That tree is about 18 years old at that height. The calculator above can do this math for you: open the “Count the rings” mode.

Frequently Asked Questions About Tree Age

How old is a tree with 73 rings?

A tree with 73 annual rings is about 73 years old, because a tree adds one growth ring each year. Counting the rings on a stump or a core sample (dendrochronology) is the most precise way to age a tree.

What is the formula for a tree’s age?

For a forest tree: age = trunk diameter at 4.5 feet (in inches) x growth factor. For example, a sugar maple 20 inches across x 5.0 = 100 years. The calculator shows it as a range, about 80 to 130 years. Yard and street trees grow faster, so for them the calculator uses U.S. Forest Service equations from city trees of known age.

How do I find a tree’s age from its circumference?

Divide the circumference by 3.14 to get the diameter, then use the calculator or the tree age chart. For example, a trunk 94 inches around is about 30 inches across. A red oak that size is about 40 to 75 years old in a yard. Pick “Around the trunk” in the calculator, and it does the math for you.

Can I tell a tree’s age without cutting it down?

Yes. Measure the trunk and use this calculator, take a core sample, count the branch whorls on a young pine, or check the planting records. See how to tell how old a tree is.

How accurate is this tree age calculator?

This calculator gives a rough estimate. That is why it shows a range. For yard and street trees, it uses a U.S. Forest Service study that measured city trees of known age in Charlotte, NC and Queens, NY. The low number is how fast the tree grew in Charlotte, and the high number is Queens. For forest trees, it multiplies trunk width by a growth factor from the published Purdue University chart where one exists; the other factors are Grant Brothers estimates. Real trees grow at uneven rates, even trees in the same yard, and the biggest tree is not always the oldest (USDA Forest Service). Soil quality, climate, competition, and human interventions all change growth. A ring count on a stump or a core sample gives the exact age.

Why is my yard tree younger than the chart says?

Growth factor charts come from trees in forests. Trees in yards and along streets get more sun and room, so they grow faster. Purdue University says forest trees grow in trunk size at about half the rate of open-grown trees. For yard and street trees, we use the U.S. Forest Service Urban Tree Database, which measured city trees of known age.

What is DBH and how do I measure it correctly?

DBH (Diameter at Breast Height) is the standard forestry measurement of tree trunk diameter taken at 4.5 feet (1.37 meters) above ground level. To measure it correctly:

1. Use a flexible measuring tape to measure the circumference at 4.5 feet above the ground.
2. Divide this circumference by 3.14 (π) to get the diameter. Or pick “Around the trunk” in the calculator above, and it does this step for you. For odd trunks, use our Tree Diameter Calculator.
3. For trees on slopes, measure from the uphill side.
4. For trees that fork below 4.5 feet, measure the narrowest point of the single trunk below the fork. This gives a rough age only.

Why does tree species matter when determining age?

Different tree species have inherently different growth rates based on their genetics and physiological characteristics. For example, in the woods a white oak 24 inches across (growth factor 5.0) is about 95 to 155 years old, while a silver maple the same size (growth factor 3.0) is about 60 to 95 years old. Each species has a specific “growth factor” that relates its diameter to its approximate age. By selecting the correct species, our calculator uses that tree’s own growth data for more accurate results.

How do growing conditions affect tree age calculations?

Environmental conditions significantly impact how quickly trees grow. Trees in optimal conditions (fertile soil, adequate water, full sun) grow faster than trees in challenging conditions (poor soil, drought, shade). The biggest difference is where the tree grows. Yard and street trees get more sun and room, so they grow faster than trees in a forest or crowded woods. That is why our calculator asks “Where does it grow?” and shows a range for each choice. Trees in challenging conditions typically grow slower and may be older than their size suggests.

Which is more reliable for tree age: trunk width (DBH) or height?

The DBH (trunk diameter) method is generally more reliable for estimating tree age because trunk diameter increases more predictably over a tree’s lifetime. As trees mature, height growth often slows or stops while the trunk continues to expand. That is why this calculator uses trunk width (DBH) only. For the most accurate results, professional arborists often consider multiple factors including DBH, height, species, and where the tree grows.

Who keeps this calculator up to date?

The Grant Brothers Tree Service arborist team. Our team includes ISA Certified Arborists, TRAQ-qualified tree risk assessors and CTSP-certified safety professionals, and Grant Brothers is led by Virginia’s first ATCP-Certified Professional Arborist (#5 in the U.S.). The yard ranges come from the U.S. Forest Service Urban Tree Database, and the forest ranges from published growth factors (sources below). Last checked: October 19, 2026.

Sources

McPherson, van Doorn and Peper, Urban Tree Database, USDA Forest Service Research Data Archive, 2016 (ages of city trees of known age: Charlotte, NC and Queens, NY; live oak: Orlando, FL and Charleston, SC)
Purdue Landscape Report, How Old Is My Tree?, 2018 (growth factor method, yard vs woodland growth, ring counts, nursery age)
Minnesota DNR, How Old Is Your Tree? (growth factor chart)
DeYoung, Forest Measurements: An Applied Approach, OpenOregon (branch whorls, ring counts, increment borers)
USDA Forest Service, Treesearch (tree growth varies, even in the same yard)

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