--- title: "Measure a tree with its shadow" published: "2026-10-15" updated: "2026-10-15" author: "Dad Field Manual editors (drafted with AI help)" time: "45 min" cost: "$0" ages: "8 and up" where: "A level yard or park on a sunny day, when the tree's shadow falls on open ground." topics: ["classic-skills","outdoors"] print: "https://dadfieldmanual.com/print?p=measure-a-tree-by-shadow" url: "https://dadfieldmanual.com/plans/measure-a-tree-by-shadow/" --- # 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. ## What you need - A straight stick or broom handle about 3 feet long (have) - A tape measure or a 3-foot piece of string to measure with (have) - Chalk, small stones or sticks to mark shadow tips (free) - Paper, pencil and a phone calculator (have) ## 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 1. **Pick a sunny day and a level spot** (Dad) Choose 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. 2. **Stand the stick up** (Kid) Stand the stick straight up in the ground, or hold it upright. Measure its height and write it down. Say, a 3-foot stick. 3. **Measure the stick's shadow** (Kid) Mark 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. 4. **Measure the tree's shadow, now** (Together) Right 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. 5. **Work out the height** (Together) Tree 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. 6. **Compare guesses** (Together) Before you measure, have each person guess the tree's height. Who came closest? Then measure something else, such as a lamppost or a house. ## 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. - Cloudy days won't work. Wait for a bright one. ## Variations - **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. ## Sources - **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. (checked 2026-10-15) - **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. (checked 2026-10-15)