How to measure tree height: 3 ways that work from a Northwest yard

How to measure tree height: three methods compared

All three methods use the same idea: a small triangle you can measure stands in for the big one you can’t. Pick by what you have on hand and how exact you need to be.

Methods: American Forests, Measuring Guidelines Handbook; PNW Extension, Basic Forest Inventory Techniques (PNW 630).

Forest Service crews who built the Urban Tree Database measured height with a clinometer or sonar device, from ground level to the treetop to the nearest half meter, leaving out an erratic leader. American Forests’ champion-tree handbook says experienced measurers with accurately calibrated, high-performance equipment can get within 2 feet. In a yard, the errors covered below matter more than the tool.

Measuring tree height with a stick

1. Set the stick to your reachHold your arm straight out and grip a straight stick so the part showing above your fist is as long as the distance from your eye to your fist.
2. Hold it upright at arm’s lengthKeep your arm straight and the stick vertical, as if it were a plumb line.
3. Back up until it covers the treeWalk forward or back until the stick, from the top of your fist to its tip, just covers the tree from its base to its top.
4. Measure your distance to the trunkTape or pace the level distance from where you stand to the trunk. That distance is the tree’s height.

American Forests’ champion-tree handbook gives the eye-level version of the same trick: hold the top of your fist at eye level, back up until the stick tip meets the treetop, and your distance to the trunk equals the height above your eyes. Add your eye height to finish.

The stick method’s errors come from a tipped stick, a bent elbow and an uneven pace count, so repeat it two or three times and average the results.

Measuring tree height with its shadow

1. Pick a sunny moment on level groundYou need a shadow tip you can find, falling on ground about as level as the tree’s base.
2. Measure the tree’s shadowTape from the middle of the trunk to the tip of the top’s shadow.
3. Measure a stick and its shadow right awayStand a yardstick or straight stick upright and measure its height and its shadow within a few minutes of the first reading, before the sun moves.
4. Do the mathHeight = tree’s shadow × stick height ÷ stick’s shadow. A 60-foot tree shadow with a 4-foot stick casting a 3-foot shadow means an 80-foot tree.

Shadows only work on flat ground: a shadow falling downhill stretches and one falling uphill shrinks. Low winter sun throws long shadows whose tips are hard to find, and a broad crown’s shadow tip may not come from the highest twig.

Measuring tree height with a clinometer or phone app

A clinometer reads the angle of your sight line. Forestry clinometers commonly show percent on one side of the scale and degrees on the other, and phone clinometer apps read degrees. PNW 630, the forest inventory guide Oregon State, Washington State and the University of Idaho publish for woodland owners, uses the percent scale.

1. Back up a measured, level distanceStand where you can see the top, ideally about as far from the trunk as the tree is tall. PNW 630 suggests exactly 100 feet when you read percent, because it makes the math easy.
2. Sight the topLine the clinometer’s mark up with the very top and read the angle.
3. Sight the baseRead the angle to the base of the trunk. Below eye level it reads negative.
4. Combine the readingsPercent: subtract the base reading from the top reading (subtracting a negative adds it) and multiply by distance ÷ 100. Degrees: height = distance × (tan of top − tan of base).

PNW 630’s worked example: from 100 feet, the top reads 90 percent and the base 5 percent below level, for a combined 95 percent and a 95-foot tree. In degrees, the same readings are about 42 and −2.9.

If you sight only the top, add your eye height, measured standing in your shoes. From 100 feet at 42 degrees, that is 90 feet plus eye height. A laser rangefinder opens up the sine method, which American Forests calls the simplest and most direct way to get height when the laser can see both top and base.

Tree height calculator

Use the angle method, the shadow method or both. Leave the base angle blank to use your eye height instead. The big number follows the method you typed in last.

How to get an accurate tree height: distance, slope, lean and the true top

Stand back about as far as the tree is tall

Angle errors grow fast at steep sight lines. Misreading by 1 degree changes the answer by about 3.5 percent when the top sits at 45 degrees, about 4 percent at 30 or 60 degrees, and about 10 percent at 80 degrees, so standing too close is an easy way to get a wildly wrong answer.

On a slope, sight both ends

Reading the top and the base takes care of sloping ground without eye height. PNW 630 advises measuring from about the tree’s own ground level and correcting the horizontal distance if you move well up or down slope: a 100-foot tape laid along a 15-degree slope covers only 96.6 feet of level ground, and along a 30-degree slope only 86.6. American Forests measures from the base at mid-slope, where the seed is judged to have landed.

Find the true top

On a Douglas fir or other conifer, the top is the leader. On a broad maple or oak, the highest twig is often not over the trunk, and American Forests warns that the plain tangent method then gives the same answer for trees of different heights. Its fix: find the spot on the ground directly beneath the top and measure your distance to that spot. Say you stand 60 feet from the trunk and the highest twig sits 10 feet closer to you: measuring to the trunk turns a true 50 feet above eye level into 60.

Decide what counts as the top before you start. Forest Service crews building the Urban Tree Database left out an erratic leader, and i-Tree records total height to the top, alive or dead, with height to the live top as a separate measurement.

Leaning trees

Height is vertical. A trunk 100 feet long that leans 15 degrees stands 96.6 feet tall, with its top 25.9 feet out from the base. If it falls, it swings from the base, so it can reach the full 100 feet. Measure your distance to the point under the top, and see the leaning tree guide for when a lean is a warning sign.

Why tree height matters: cost, drop zone and power lines

This site’s modeled removal costs are built on four height bands, so height is the first number to bring to a quote. Each band also sets how much open ground a felling needs: OSHA’s hazard bulletin for tree crews says to keep ground workers at least two tree heights from a tree being felled.

Modeled estimate, not quotes (method). Clear ground: OSHA Hazard Bulletin HB-3731 (2014); workers on a rope used to fell the tree must be at least one and a half tree heights away.

Your measured height plugs straight into the tree removal cost calculator, and the band-by-band breakdown is on tree removal cost. Cal/OSHA’s tree work guide adds that people should stand even farther back on slopes, where logs can roll or slide.

Height also tells you what a tree could hit. A tree can reach anything within its own height of the trunk, so compare your number with the distance to the house, garage and fence; the guide to whether a tree is too close to your house walks through it.

Power lines: Oregon OSHA’s rule OAR 437-002-0306 requires that the power company be notified when tree work comes within 10 feet of a power line or a tree may fall within 10 feet of one, and Washington treats tree work within 10 feet of lines as line-clearance work (WAC 296-45-035). If your tree is taller than its distance to the line minus 10 feet, only the utility or a qualified line-clearance crew should cut it; see tree removal near power lines.

For trees that size, see what large tree removal involves; if you plan to drop a small one yourself, start with how to cut down a tree.

How tall do Northwest trees get?

Knowing what to expect helps you catch a bad reading. USDA’s PLANTS database lists how tall a species can be at 20 years and its mature height, and i-Tree sorts trees into small (40 feet or less at maturity), medium (41 to 60 feet) and large (over 60 feet).

Sources: USDA NRCS PLANTS Database, species characteristics (height at 20 years, maximum; mature height); size classes apply the height cutoffs in USDA Forest Service, Understanding i-Tree (GTR-NRS-200-2021), to the PLANTS mature heights. Species-level values; cultivars, sites and individual trees vary, and other references differ (compare the OSU mature heights in the guide to whether a tree is too close to your house).

Forest-grown natives go far higher. The Forest Service silvics manual calls old-growth Douglas firs 250 feet tall common and records one near Little Rock, Washington, at 330 feet; ponderosa pine commonly reaches 90 to 130 feet, while shore pine on the coast stays at 20 to 40. In Portland, the city’s heritage giant sequoias measure 95 to 200 feet tall. Height says little about age; for that, see how old is my tree, and for the region’s signature conifer, Douglas fir.