Tree Diameter (DBH) Calculator
Turn trunk circumference into diameter at breast height in inches, centimetres and feet, plus basal area, Doyle log scale and a size class.
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Tree Height Calculator
Estimate a tree's height from its shadow using a reference object and similar triangles, with the current sun angle and a height class.
Tree Height Calculator
Chlorova · updated for 2026
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This is a similar-triangles estimate, accurate when the ground is level, the tree stands plumb and its shadow falls wholly on flat open ground. A tree on a hillside, a crooked trunk, or a shadow that runs up a wall or over a hedge will each shift the answer, sometimes by several feet. The height printed here is crown tip above the base, not clear trunk under the branches, which is the number a logger or a climbing crew actually needs. Never use any height estimate as the basis for working near a power line.
You cannot put a tape on a tree top, but the sun does the measuring for you. Because the rays arrive at the same angle to a person and to a tree standing in the same open ground, their heights and shadows form two matching triangles, and one ratio carries across. That is the oldest tree-measuring trick in forestry and it needs no clinometer, no trigonometry and no app. Measure a known object's shadow, measure the tree's shadow, and the height falls out of a division.
Measuring Height With Two Shadows
- Pick a roughly level spot where the tree throws its whole shadow on bare ground.
- Choose your reference object, ideally a person standing square or a plumb post.
- Measure the reference shadow in feet from the base to the darkest tip.
- Have someone stand still so the reading is taken in one moment, not two.
- Measure the tree shadow from the trunk base out to the topmost shadow point.
- Keep both readings in the same units, feet or fractions of feet.
- Read the estimated height, then the height class line for your work plan.
- Take a second set of readings five minutes later to bound the error.
- Average the two heights rather than trusting the luckier single pass.
Similar Triangles, One Ratio
Sunlight reaching your yard arrives at essentially one angle, so a reference object and a tree near it each make a right triangle with the same shape. Matching sides give the rule: tree height equals the tree's shadow multiplied by the reference height divided by the reference shadow. A 5.5 ft person throwing a 4 ft shadow sets a ratio of 1.375, so a 28 ft tree shadow means a 38.5 ft tree.
The same ratio is the tangent of the sun's elevation, which is why the calculator can also print the sun angle as arctangent of that ratio, and its reciprocal as shadow feet cast per foot of height. Late in the afternoon that per-foot number climbs steeply, and so does your measurement error, because a small mistake on a long soft shadow gets multiplied back into the height.
Worked Example: A 28-Foot Shadow
- Choose the person reference, since 5.5 ft is close to most adult eye-to-crown height.
- Your helper's shadow measures 4 ft on the level lawn at mid-morning.
- The ratio line prints 1.375, which is reference height over reference shadow.
- The tree shadow from trunk base to tip measures 28 ft of clear ground.
- Multiply 28 by 1.375 and the estimated height reads 38.5 ft.
- In metres that same crown tip sits at 11.73 m above the base.
- The sun elevation line returns 54 degrees, a comfortable working sun.
- Shadow per foot of height reads 0.73 ft, so a fence casts short shade here.
- The height class verdict calls it tall, meaning rigging rather than ladder.
- A second pass an hour later at 40 ft of tree shadow prints 55 ft, so recheck.
Reference Object Cheat Sheet
Pick an object whose true height you can verify, and keep both readings quick. Standard lengths below are nominal: a driven post loses inches below the soil line, and an adult's height is best measured against a door frame rather than assumed.
| Reference | Height (ft) | Best used when | Watch out for |
|---|---|---|---|
| Adult, standing square | 5.5 | Open lawn, level ground | Slouching, thick-soled boots |
| Fence post driven | 5.0 to 6.0 | Fence line already on site | Buried depth not accounted |
| Fence panel held plumb | 4.0 | Two people already there | Panel leaning, not vertical |
| Ladder stood on end | 8.0 | Tall object needs longer shadow | Wind moving the ladder |
| Vehicle roof height | 5.0 to 6.5 | No helper available | Antenna and roof rack tips |
| Garden wall or shed | verify first | Permanent vertical edge | Cap and gutter overhang |
Key Terms
- Similar triangles
- Two triangles with matching angles, so their sides share one constant ratio.
- Sun elevation
- The angle of the sun above the horizon, in degrees, at the moment you measure.
- Crown tip
- The highest live point of the tree, which is what the shadow method measures to.
- Clear trunk
- Bole height with no branches, the number a logger wants instead of total height.
- Plumb
- Perfectly vertical, the assumption every shadow reading quietly depends on.
- Drop zone
- The ground area a felled tree will cover, decided from its height and lean.
Getting a Height You Can Trust
- Mid-morning and mid-afternoon give the best shadow work, because the sun is high enough for a firm shadow edge yet low enough that the tree's shadow lands clear of obstacles.
- Around local noon the tree shadow is shortest and errors are smallest, but on a crowning tree the tip shadow goes soft and hard to place, so measure both ways and compare.
- Two readings taken minutes apart usually agree within a foot on a 40 ft tree; if they do not, the ground was not level or the shadow crossed something.
- Shadow methods measure tip height only. A tree leaning 15 degrees out of plumb gives a shadow length that understates its true vertical rise, so correct your estimate for lean before you rig.
- The reciprocal you get here, shadow feet per foot of height, is the same figure the sun exposure calculator uses to predict season-long shade, so one afternoon survey answers two questions.
Common Mistakes & Fixes
- Measuring the reference shadow and the tree shadow several minutes apart at low sun.
- Including a shadow that runs up a wall or across a hedge as if it lay flat.
- Assuming a stated adult height instead of measuring one against a door frame.
- Starting the tree measurement at the butt flare rather than the true trunk base.
- Reporting clear trunk height when the shadow only ever gives crown tip height.
- Letting a long afternoon shadow amplify a half-foot tape error into two feet of height.
When to Reach for This
Use it when you need a defensible height before quoting removal work, before ordering a crane or bucket, when a neighbor's tree shadows your garden, or when sizing a drop zone. Combine it with the diameter calculator for a volume and value picture, and with the sun exposure tool when the real question is shade rather than height.
Tree Height Calculator: Frequently Asked Questions
How do you estimate tree height from its shadow?
Divide a known object's height by its shadow, then multiply that ratio by the tree's shadow. If your 5.5 ft reference throws a 4 ft shadow, the ratio is 1.375, and a 28 ft tree shadow becomes a 38.5 ft tree. Both readings must be taken within a minute of each other.
Do I need a clinometer to measure a tree's height?
Not for the shadow method, which is why it survives in every forestry field guide. A clinometer earns its place when shadows are unusable, on steep ground, in cloud, or when you need clear trunk height rather than crown tip.
What if the tree's shadow falls on a slope or a building?
Then the shadow method is not valid for that reading, because the geometry assumes both shadows lie on the same flat plane. Wait for a time of day when the whole shadow lands on level ground, move to the other side of the tree, or switch to a clinometer method.
How accurate is shadow-ratio tree height?
A careful pair of readings on level ground usually lands within 5 to 10 percent of a measured height, which is good enough for planning removals and drop zones. The error grows fast as the sun drops, since a soft tip shadow on a long throw is difficult to place exactly.
Can I use a stick instead of a person?
Yes, and a marked stick is often better because two people cannot argue about its height the way they argue about whether someone was standing straight. Hold or set it truly vertical, measure its shadow first, and keep the shadow short enough to read to the nearest inch.
What height is too tall to handle myself?
Any tree whose crown reaches a power line, or whose falling trunk would cross a roof, a drive or a neighbour's fence, is a professional job regardless of your tools. Above roughly 60 ft the rigging, rope and branch weights stop being weekend work even for people who own chainsaws.
Sources & Further Reading
- Estimating Tree Height by Shadow and Clinometer Methods — University of Florida IFAS Extension. Similar-triangle procedure and its stated accuracy limits.
- Measuring Trees: Height, Diameter and Crown — Penn State Extension. Basis for crown-tip versus clear-bole height conventions.
- Sun Angle, Shadows and Site Survey — USDA Natural Resources Conservation Service. Shadow-per-foot-of-height relationship used in shading assessments.
Chlorova Gardening Team
Builds, checks and documents every tool we publish
Chlorova editorial review
Checked against extension-service publications
Formula verified against published references · Updated
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