A straight stick or broom handle about 3 feet longHave
A tape measure or a 3-foot piece of string to measure withHave
Chalk, small stones or sticks to mark shadow tipsFree
Paper, pencil and a phone calculatorHave
Where: A level yard or park on a sunny day, when the tree's shadow falls on open ground.
Before you start
Don't climb the tree or lean ladders on it. This plan keeps your feet on the ground.
Stay away from roads and driveways when you measure shadows. Pick a quiet spot.
If thunder rumbles, stop and go indoors. Don't finish the measurement.
02Steps
Pick a sunny day and a level spot
DadChoose level, open ground where the tree's whole shadow falls on flat ground. The best time is morning or afternoon, when shadows are long enough to measure.
Stand the stick up
KidStand the stick straight up in the ground, or hold it upright. Measure its height and write it down. Say, a 3-foot stick.
Measure the stick's shadow
KidMark the tip of the stick's shadow with a stone and measure from the base of the stick to the mark. A 3-foot stick might cast a 4½-foot shadow.
Measure the tree's shadow, now
TogetherRight away, before the sun moves, mark the tip of the tree's shadow and measure from the trunk's base to the mark. Walking heel to toe gives a rough number.
Work out the height
TogetherTree height = tree shadow × stick height ÷ stick shadow. A 45-foot tree shadow with a 3-foot stick and 4½-foot shadow gives a 30-foot tree. Check the answer by sight.
Compare guesses
TogetherBefore you measure, have each person guess the tree's height. Who came closest? Then measure something else, such as a lamppost or a house.
03If it stalls
If the stick won't stand, hold it against a post or have the kid hold it straight.
Measure both shadows within a couple of minutes. The sun moves.
Cloudy days won't work. Wait for a bright one.
04Variations
Ages 5–7
Skip the math. Lay a string the length of the tree's shadow and compare it with the string for the stick's shadow.
Ages 8–11
The full plan.
Ages 12+
Try the 1911 triangle method described on p. 64: a pole, a sighting line to the tree top, and two measured distances on the ground.
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1911 scouting handbook, pp. 64–66. The 1911 book says to measure a tree's height on level, open ground by comparing the length of its shadow with the shadow of a pole of known height, using the simple rule of proportion. It also says to estimate distance by sound by counting seconds between a sight and its sound and multiplying by 1,100 feet. Project Gutenberg (public domain in the USA) Checked Oct 15, 2026
Distance to lightning by sound. The National Weather Service says to count the seconds between the flash and the thunder and divide by 5 to get the distance in miles, and to seek shelter if thunder follows the flash within 30 seconds or less. National Weather Service Checked Oct 15, 2026
Dad Field Manual · Field card 73 · Classic Field Skills
Measure a tree with its shadow
Forty-five minutes on a sunny day. Use a stick, a tape measure and a little arithmetic to find how tall a tree is without climbing it.
Time
45 min
Cost
$0
Ages
8 and up
Where
Open ground with a tree
Since 1911: The shadow method works the same as in 1911. The sound rule needs one change: sound travels about a mile in 5 seconds, so the National Weather Service tells you to count the seconds from flash to bang and divide by 5. If thunder follows within 30 seconds, go indoors.
What you need
A straight stick or broom handle about 3 feet long
A tape measure or a 3-foot piece of string to measure with
Chalk, small stones or sticks to mark shadow tips
Paper, pencil and a phone calculator
Before you start
Don't climb the tree or lean ladders on it. This plan keeps your feet on the ground.
Stay away from roads and driveways when you measure shadows. Pick a quiet spot.
If thunder rumbles, stop and go indoors. Don't finish the measurement.
Steps
Pick a sunny day and a level spot. Choose level ground in morning or afternoon sun, with the whole tree shadow on flat ground.
Stand the stick up. Stand the stick upright and measure its height.
Measure the stick's shadow. Mark the stick's shadow tip and measure the length.
Measure the tree's shadow, now. Right away, measure the tree's shadow from the trunk base to its tip.
Work out the height. Tree height = tree shadow × stick height ÷ stick shadow.
Compare guesses. Compare the guesses with the answer and measure a second object.
If it stalls
If the stick won't stand, hold it against a post or have the kid hold it straight.
Measure both shadows within a couple of minutes. The sun moves.
