The tree height calculator above turns a horizontal distance and two sightings — one to the top of the tree, one to its base — into total height. It handles the three field methods people actually use: a forestry clinometer read on its percent scale, plain angles in degrees from a clinometer or a phone inclinometer, and the old stick method that needs no instrument at all. It also applies the two corrections that field guides insist on and beginners skip: converting a slope distance to a horizontal distance, and adding the part of the tree that sits below your eye.
Arb Digital publishes this as a field-measurement tool. It is deliberately narrow — it measures the vertical dimension of one tree and nothing else. It does not estimate age, value, canopy or crowding, and it makes no judgement about whether a tree is safe to stand under.
What This Tree Height Calculator Does
Every method here rests on the same piece of trigonometry: from a known horizontal distance, the tangent of the angle to a point tells you how far above or below eye level that point is. Sight the top, sight the base, and the difference between those two vertical offsets is the height of the tree. Because you are almost never standing exactly level with the tree's foot, the base sighting is not optional — it is what makes the answer correct on sloping ground.
The percent scale on a standard forestry clinometer is a convenience that removes the trigonometry entirely. Iowa State University's guide to measuring tree height using a clinometer describes the arrangement plainly: at a baseline of 100 feet, the percent reading is the height in feet directly, and at other distances the reading scales with the distance. The percent scale is simply the tangent of the angle multiplied by one hundred.
Boundary in one sentence: this page measures total height, ground to the highest live point. Merchantable height, crown length and live-crown ratio are separate quantities defined in the University of Tennessee Extension guide A Simple Guide to Common Forest Measurements, and they are read off the same sightings but stop at different points on the stem.
How to Use It
- Pick your method. Percent scale if you have a forestry clinometer, degrees if you are using an app or a transit, stick method if you have neither.
- Pace or tape the distance to the tree and enter it. If the ground between you and the tree slopes, enter the slope angle too and the tool converts your slope distance into the horizontal distance the trigonometry actually needs.
- Sight the top and read it, then sight the base of the trunk where it meets the ground and read that. Enter the base reading as a negative number if the foot of the tree is below your eye.
- For the stick method, enter the stick length, the eye-to-stick distance and your eye height instead of angles.
- Read the total height, and check the split between the part above and below eye level — if the below-eye figure looks wrong, your base sighting probably is.
The Formula and How It Is Calculated
With the percent scale and a horizontal distance D:
Height = D × (top reading − base reading) ÷ 100
Worked example, which is the default loaded above: standing 100 feet from the tree on level ground, the top reads +72 per cent and the base reads −8 per cent. Height = 100 × (72 − (−8)) ÷ 100 = 80 feet. Note the subtraction of a negative number — the eight feet below your eye is added to the height, and treating that reading as positive would give 64 feet and understate the tree by a fifth.
In degrees the same calculation is Height = D × (tan θtop − tan θbase). Checking it against the same example: an angle of 35.75° has a tangent of 0.7199 and an angle of −4.57° has a tangent of −0.0799, so the height is 100 × 0.7998 = 79.98 feet, the same 80-foot tree.
The stick method uses similar triangles instead. Hold a stick upright at arm's length so that its top lines up with the top of the tree and its bottom with the base, and the ratio of stick length to eye-to-stick distance equals the ratio of tree height to your distance from the tree. So Height above eye = D × (stick length ÷ eye-to-stick distance), and your eye height is added to reach the ground. A 12-inch stick held 24 inches from the eye at 100 feet from the tree gives 50 feet above the eye, plus a 5.5-foot eye height, so 55.5 feet in total.
Slope correction is the last piece. If you measured your distance along sloping ground, the horizontal distance is slope distance × cos(slope angle). On a 20-degree slope, a 100-foot paced distance is only 94 horizontal feet, so using the raw pace count would overstate the tree by about six per cent.
Why Two Sightings, Not One
The most common shortcut is to sight only the top and assume the base is at eye level. That is true only when you are standing on ground at exactly the same elevation as the tree's foot, which is rare outside a mown lawn. Uphill of the tree, the base sits below your eye and a single sighting understates the height. Downhill, the base sits above your eye and a single sighting overstates it, sometimes badly.
The two-sighting method fixes this automatically because it measures the vertical distance from your eye to the top and from your eye to the base, then adds or subtracts as the signs demand. It is also why the tool asks you to enter a negative base reading rather than an absolute value: the sign carries real information about where you are standing relative to the tree.
Standing in the Right Place
Distance matters for accuracy, not just for the arithmetic. Too close and the angle to the top becomes steep, where a small reading error translates into a large height error because the tangent function is changing quickly. Too close also makes it very hard to see the actual top of the tree through the crown, which is the dominant source of error on broadleaved species with rounded, irregular canopies.
A reasonable working rule used across field guides is to stand at a distance roughly equal to the tree's height, which puts the top sighting near 45 degrees, and then to move back further if the crown obscures the top. On a leaning tree, stand at right angles to the direction of lean; measuring along the lean produces an answer that is neither the height nor the length of the stem.
The instrument matters less than the discipline. A laser hypsometer, a clinometer and a phone inclinometer will all give similar answers to a careful observer standing in a good position, and all three will give bad answers from a poor position. Repeat the measurement from a second spot and compare — if the two disagree by more than a few per cent, one of your sightings found the wrong branch.
Total Height, Merchantable Height and Crown Length
Total height runs from ground level to the highest point of the crown. Merchantable height stops where the stem is no longer usable for the product in question; the Tennessee guide notes that for hardwood sawtimber this is commonly where the diameter inside bark at the small end reaches 10 inches, and that merchantable height is conventionally counted in 16-foot log lengths. Crown length is the portion of total height carrying live branches, and the ratio of crown length to total height is used as an indicator of vigour.
All three come from the same sightings; you simply read a different point on the stem. If you want the wood volume that follows from merchantable height, that requires a log rule and a form class rather than height alone, and our board foot calculator handles the lumber side of that arithmetic once the volume is known.
Arb Digital publishes hundreds of free, no-signup tools covering forestry, biology, science, finance and everyday maths — no accounts, no stored data.
Browse All Free Tools Contact Arb DigitalCommon Mistakes to Avoid
- Sighting only the top. Without a base sighting the answer is only correct on perfectly level ground, and you have no way of knowing how far off it is.
- Entering the base reading as a positive number when the tree's foot is below your eye. This subtracts the lower part of the tree instead of adding it.
- Using a paced slope distance as if it were horizontal. On steep ground this inflates every height you record.
- Standing too close, which magnifies angle error and hides the true top behind nearer branches.
- Measuring a leaning tree along the lean, which returns neither the vertical height nor the stem length. Move round to the side first.
Related Free Tools From Arb Digital
Height pairs with diameter in almost every forestry calculation, and our tree diameter calculator converts a tape reading into DBH and basal area. From there the tree age calculator estimates age from published growth data and the tree value calculator runs the trunk-formula appraisal method. For canopy questions see the tree leaf count calculator and the tree spacing calculator, and at stand level the forest basal area calculator. The tree benefits calculator scales published benefit rates across a planting. Browse the full free online tools hub for more.
Frequently Asked Questions
Stand a measured horizontal distance from the tree, read the percent scale sighting the top, then read it again sighting the base. Multiply the difference between the two readings by the distance and divide by one hundred.
Because you are rarely standing level with the foot of the tree. The base sighting measures how far the tree's base sits above or below your eye, and without it the answer is only correct on perfectly flat ground.
The trigonometry needs a horizontal distance. If you paced along a slope, multiply the slope distance by the cosine of the slope angle. On a twenty-degree slope a hundred paced feet is about ninety-four horizontal feet.
Hold a stick upright at arm's length so its top aligns with the tree's top and its base with the tree's base. The ratio of stick length to eye-to-stick distance equals the ratio of height above your eye to your distance from the tree; add your eye height for the total.
Roughly the height of the tree is a common working rule, which puts the top sighting near forty-five degrees. Move further back if branches hide the actual top, since a wrong top sighting is a bigger error than a slightly flatter angle.
No. Total height runs from the ground to the highest point of the crown. Merchantable height stops where the stem is no longer usable for the intended product and is conventionally counted in sixteen-foot log lengths.
A phone inclinometer gives angles in degrees, which this calculator accepts directly. The limiting factor is usually how steadily you can hold the phone and whether you can see the true top of the crown, not the instrument's resolution.
This calculator performs published field-measurement arithmetic for general and educational use. It does not assess tree condition or stability. Work near, under or in a tree carries real risk, and any decision about a tree's safety or removal should come from a qualified forester or an ISA Certified Arborist who has inspected it.
