Tree Height Calculator

Estimate a tree's height from your horizontal distance to it, the angle up to the treetop, and your eye height, using the tangent (clinometer) method.

Quick Facts

Method
Tangent method: height = distance × tan(angle) + eye height
Best on flat ground with a clear sight line to the true top of the tree.

Your Results

Calculated
Estimated tree height
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Base of trunk to top
Height above your eye
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distance × tan(angle)
Height in feet
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1 m = 3.28084 ft
Line-of-sight distance
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Eye to treetop

Ready

Enter your distance, angle, and eye height, then calculate.

How to estimate tree height with the tangent method

You can measure how tall a tree is without climbing it or dropping a tape from the top. The standard field technique is the tangent method, which uses simple trigonometry. Stand a known horizontal distance from the trunk, sight the very top of the tree, and measure the angle your line of sight makes above horizontal. The tree's height above your eye is then the distance multiplied by the tangent of that angle. Because your eye sits above the ground, you add your eye height to get the full height from the base of the trunk.

The formula

Height = d × tan(θ) + h, where d is the horizontal distance from you to the base of the tree, θ is the angle of elevation from your eye to the treetop, and h is the height of your eye above the ground. The tangent function is what a clinometer, a builder's inclinometer, or a phone level app effectively measures. If you record the angle in degrees, remember that most calculators expect radians, so convert with radians = degrees × π / 180 before taking the tangent.

A worked example

Suppose you stand 20 m from the trunk on level ground, your eye is 1.6 m off the ground, and you measure the angle to the top as 35°. Then tan(35°) ≈ 0.7002, so the height above your eye is 20 × 0.7002 = 14.00 m, and the full tree height is 14.00 + 1.6 = 15.6 m (about 51 ft). Doubling your distance to 40 m at the same tree would roughly halve the angle you measure, and the computed height stays the same — a good built-in consistency check.

Why the distance and angle both matter

  • The angle alone tells you nothing about height — a 45° sighting means the top is one horizontal distance up, whether you are 5 m or 50 m away.
  • Measuring from farther back reduces the effect of small angle errors, but you need a clear sight line to the actual top.
  • A 45° angle is the sweet spot: at 45° the height above your eye simply equals your distance to the tree, and measurement error is minimized. Position yourself so the angle is roughly 30°–45° when practical.

Common reference points

For context: a mature backyard oak or maple is often 15–25 m (50–80 ft); a typical two-story house is about 6 m (20 ft) to the eaves; coast redwoods (Sequoia sempervirens), the tallest trees on Earth, exceed 100 m, with the record tree "Hyperion" measured at about 116 m (380 ft). If your estimate lands wildly outside the plausible range for the species and setting, re-check your distance and angle before trusting it.

Frequently Asked Questions

How do you measure a tree's height without climbing it?
Stand back a measured horizontal distance from the trunk, then measure the angle from your eye up to the very top of the tree using a clinometer or a phone app. The height above your eye is distance × tan(angle). Add your eye height above the ground to get the full tree height.
Why do I add my eye height to the result?
The angle is measured from your eye, which sits above ground level. The tangent method gives the height of the treetop above your eye, so you must add the height of your eye above the ground (typically about 1.5 m or 5 ft) to get the true height from the base of the trunk.
What if the ground is not flat?
On sloping ground the simple tangent formula introduces error, because the base of the tree is not at the same level as your feet. For sloped sites, foresters measure two angles — one to the top and one to the base of the tree — and add or subtract the two computed heights. This calculator assumes you and the base of the tree are on roughly level ground.
How accurate is the tangent method?
On flat ground with a clear line of sight to the true top, it is typically accurate to within a few percent. The biggest errors come from sighting the wrong point in the canopy, a leaning tree whose top is not above its base, or sloping terrain. It is a reliable quick field estimate, not a survey-grade measurement.

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