Tree height calculator

Built by Nitin Raja · Last updated October 24, 2026

How to measure the height of a tree with your phone

Foresters measure trees with a clinometer, a small tool that shows the angle from your eye to the top of the tree. Your phone has the same thing built in: the motion sensor that rotates the screen knows exactly how far the phone is tilted. This page turns that sensor into a clinometer, with the camera as a sight, so you can measure a tree, a house, a flagpole or any tall object without climbing it or downloading an app.

Step by step

1. Stand back. Walk away from the trunk until you can see the whole tree clearly, top and bottom. About one tree-height away is ideal: the angle to the top is then around 45 degrees, where small aiming errors matter least.
2. Choose how to scale it. If you can measure or pace your distance to the trunk, enter it. If not, choose Use my eye height and enter your own height (or measure it with the camera button). The page uses your eye level as the known length instead.
3. Tap Start and allow motion and camera access when your browser asks.
4. Aim at the top. Hold the phone upright, line up the crosshair with the very top of the tree, keep still for a moment and tap Lock top.
5. Aim at the base where the trunk meets the ground and tap Lock base. The height appears straight away.

How the maths works

The angle to the top and the angle to the base, together with your distance, form two right-angled triangles. The height above your eyes is the distance times the tangent of the top angle, and the part below your eyes is the distance times the tangent of the base angle. Add them and you have the full height, with no need to know your eye height. In eye-height mode it works the other way round: your eyes are about 94% of your body height above the ground, so the angle down to the base tells the page how far away you are.

Tips for an accurate reading

• Find the true top. On broad trees the highest point is often behind the front branches. Walk around until you can see the leader, the topmost shoot.
• Flat ground helps, especially in eye-height mode. If the tree is uphill or downhill, use a measured distance instead and lock both angles.
• Leaning trees: measure your distance to the point directly under the top, not to the trunk.
• Measure twice from different spots and average the results.

The shadow method

No phone sensor? On a sunny day, measure your own shadow and the tree's shadow at the same time. Because the sun hits both at the same angle, the ratio of height to shadow is the same: tree height equals the tree's shadow times your height divided by your shadow. It works best in the morning or afternoon, when shadows are long and easy to measure.

Houses, buildings and flagpoles

The same method works for anything tall. For a house, aim at the roof ridge if you can see it; up close you may only see the gutter. For a flagpole, aim at the top of the pole, not the flag. If you are measuring something for a permit or for work near power lines, use a professional measurement; this tool is for estimates.

Why we built this tree height calculator

Foresters measure tree height with a clinometer and a tape: the angle to the top, the angle to the base and the distance to the trunk. Most people who want to know how tall the tree in their garden is own neither tool, and climbing or guessing is not a measurement. A phone already has the sensor that matters, the one that rotates the screen, and it knows its tilt to a fraction of a degree.

Two practical problems remain, and we built the page around them. Often you cannot measure your distance to the trunk, so there is an eye-height mode that uses your own height as the known length instead. And laptops have no tilt sensor at all, so the page also has the shadow method and a plain angle calculator for readings taken with a real clinometer.

What this tree height calculator measures

In phone mode it reads the motion sensor, averages the tilt over the last 0.4 seconds, and turns it into an angle above or below the horizon (the phone's front-back tilt minus 90 degrees, held upright). It refuses to lock an angle if the reading moved by more than 2 degrees in that time, so a shaky hand does not get recorded. Then:

• With a distance: height = distance x (tan of the top angle - tan of the base angle).
• With your eye height: eyes are taken as 0.937 x your height (Pheasant and Haslegrave, Bodyspace), distance = eye height / tan of the angle down to the base, then the same formula. The base must be below eye level.
• Shadow method: height = its shadow x your height / your shadow.
• Angle calculator: height = distance x tan(angle) + eye height.

The result shows the distance and both angles it used, and warns you when the top angle is above 70 degrees (step back) or, in eye-height mode, when the base is less than 3 degrees below your eyes. The rear camera is only a sight for aiming: the picture is shown on your screen, not recorded or uploaded. Last checked 24 October 2026. What it does not measure: where the true top of the tree is (you aim at it), slopes between you and the trunk, how much a tree leans, or the distance itself. It is an estimate, not a survey for permits or work near power lines.

Why this tree height calculator is different

• No app, no clinometer. It runs in the phone's browser with the sensor it already has.
• No tape needed in eye-height mode, and a camera height check for your own height if you do not know it.
• Three methods, so it still works on a computer or on a sunny day without a phone.
• A steadiness check before an angle is locked, and the angles and distance are printed with the result so you can check the maths.
• It starts empty and shows a height only after you have locked both angles. Free, no account.

Want to know how tall you are first? Measure your height with the same phone, or measure smaller objects up close.