Free Tree Height Calculator - Shadow Method
Estimate the height of a tree using the similar triangles shadow method. No climbing required.
Enter your height, your shadow, and the tree's shadow to estimate tree height.
The Tree Height Calculator estimates how tall a tree is from three measurements: your height, your shadow length, and the tree’s shadow length. It uses the same similar-triangles logic behind several simple field methods for measuring tall objects from the ground, including stick-and-sight methods taught by forestry extension programs for measuring tree height without climbing or cutting the tree using a right triangle.
This is a practical calculator for homeowners, students, gardeners, landowners, and anyone who needs a reasonable height estimate before making a next decision. It can help you compare a tree with a roofline, estimate whether a young shade tree is growing as expected, gather a rough number before using the /tools/tree-removal-cost-calculator/, or add context to measurements from the /tools/tree-diameter-calculator/ and /tools/dbh-basal-area-calculator/.
The shadow method is useful because it is fast, free, and easy to repeat. It is not a professional tree inventory method, a safety inspection, or a substitute for a certified arborist when the tree is near a house, road, utility line, or target. Treat the result as a field estimate: strong enough for planning and learning, but limited by sun angle, slope, tree shape, and the quality of your measurements.
The calculator turns a shadow comparison into an estimated tree height. If a 6-foot person casts an 8-foot shadow at the same moment a tree casts a 64-foot shadow, the tree is estimated at 48 feet tall. The calculator is doing that proportion for you so the units stay consistent and the arithmetic does not get in the way.
The key condition is that both shadows must be measured at the same time, on the same general surface, under the same sun. The sun is far enough away that its light reaches the person and the tree at nearly the same angle, so the height-to-shadow relationship is shared. When the ground is level and both objects are vertical, the ratio of height to shadow length is a useful shortcut.
The calculator does not identify species, judge whether a tree is hazardous, estimate wood volume, or measure merchantable log height. If you are estimating timber, removal complexity, pruning access, or carbon storage, tree height is only one input. Pair it with diameter, species, crown condition, site access, and professional judgment where the decision has financial or safety consequences.
The formula is simple:
Tree height = (your height / your shadow length) x tree shadow length
All three input measurements must use the same unit. Feet, inches, meters, or centimeters can all work, but do not mix feet for your height with meters for the tree shadow. If your height is in feet and your shadow is in feet, the result is in feet. If your measurements are in meters, the result is in meters.
The formula works because similar triangles have matching angle relationships and proportional side lengths. Forestry measurement has long used geometry and trigonometry for tree height work; USDA Forest Service research notes that height-measuring instruments have historically used similar triangles, angles, distances, and hypsometer methods to estimate total tree height from the ground.
Imagine your body and its shadow as one triangle: your height is the vertical side, your shadow is the ground side, and sunlight forms the slanted side. The tree and its shadow create a larger triangle with the same sun angle. If both triangles are sitting on level ground, the smaller triangle becomes a scale model of the larger one.
That is why the exact time of day matters less than matching the measurements. You do not need to know the sun’s angle in degrees if you measure your shadow and the tree’s shadow at the same moment. Your body becomes the reference object, and the tree is scaled from that reference.
The method breaks down when the triangles stop matching. A sloped lawn tilts one triangle. A leaning tree moves the top away from the base. A shadow that runs across a curb, planting bed, ditch, wall, or fence changes the measured ground distance. A broken or hidden shadow tip makes the tree shadow too short. The calculator cannot see those problems, so the person measuring has to catch them.
Measure your height first, ideally with shoes similar to the ones you will wear outside. If you enter your barefoot height but stand outside in boots, the difference is usually small, but it is still unnecessary error. A tape measure, yardstick, or marked wall is enough.
Next, measure your shadow from the point directly below your feet to the tip of the shadow cast by the top of your head. This is easier with a helper. Stand straight, keep your posture natural, and mark the head-shadow tip with a small object before the sun shifts. If you are alone, use a phone timer or a small stake so you are not trying to bend, mark, and measure at the same time.
Finally, measure the tree shadow from the base of the trunk to the farthest visible tip of the shadow cast by the top of the tree. For a narrow conifer, this may be fairly obvious. For a broad deciduous tree, the highest twig is not always above the center of the trunk, and the farthest shadow may come from a side branch rather than the true top. That is one reason broad, irregular crowns are harder to measure cleanly than upright trees.
Pick a sunny period when the tree casts a clear shadow on open ground. The shadow tip should be visible enough that two people would mark almost the same point. If the shadow fades into another tree’s shade, crosses a driveway edge, or disappears into shrubs, choose another time or another method.
Use a tape measure for the tree shadow if possible. Pacing can work for rough estimates, but every uneven step adds error, and that error scales up with the tree. A 2-foot mistake on a 20-foot shadow is a much larger percentage error than a 2-foot mistake on an 80-foot shadow, so write down both the measurement and how confident you are in it.
Take your own shadow and the tree shadow immediately, not ten or fifteen minutes apart. Shadows move and change length continuously through the day. If a helper is available, have one person mark the body shadow while the other marks the tree shadow, then measure both marks after they are fixed.
The cleanest shadow readings usually happen when the sun is high enough to make shadows manageable but not so high that the shadow is too short to mark accurately. Around local solar noon, the sun crosses the observer’s meridian, and NOAA notes that a vertical pole’s shadow points north or south at solar noon depending on location and season at solar noon. This is often a good reference point because shadows are comparatively short and consistent.
Clock noon is not always solar noon. Time zone position, daylight saving time, and longitude inside a time zone can shift the actual solar-noon moment. NOAA’s solar tools can calculate sunrise, sunset, solar noon, and solar position for a selected place for any place, which is helpful if you are making repeated measurements for a school project, tree record, or property inventory.
Avoid very early morning and late afternoon when shadows are long, stretched across obstacles, and sensitive to small marking errors. Long shadows are not automatically wrong, but they are harder to measure. A tiny uncertainty at the shadow tip can become a large change in estimated height.
Suppose you are 5.75 feet tall, your shadow is 7.5 feet, and the tree shadow is 62 feet. The formula is:
(5.75 / 7.5) x 62 = 47.5 feet
The calculator would estimate the tree at about 47.5 feet tall. For ordinary yard planning, you might round that to 48 feet because the shadow tip, tree top, and ground level probably carry more uncertainty than the decimal place suggests. A result like 47.53 feet looks precise, but the field measurement may only justify a range such as 46 to 50 feet.
Now rerun the same example with a tree shadow of 66 feet instead of 62 feet. The estimate becomes 50.6 feet. That small field difference changes the result by a little over 3 feet, which shows why the tree-shadow measurement deserves the most attention. Your height is usually known; the tree shadow is the moving target.
Imagine a young ornamental tree in a front yard. You are 68 inches tall, your shadow is 54 inches, and the tree shadow is 216 inches. The calculator gives:
(68 / 54) x 216 = 272 inches
Convert 272 inches to feet by dividing by 12, and the tree is about 22.7 feet tall. That is a useful number if you are tracking growth, comparing a tree with mature-size expectations, or deciding whether the tree still fits under nearby overhead space.
This example also shows why inches can be convenient for shorter trees. If you measure everything in inches, the calculator returns inches. You can convert afterward, or you can convert all inputs to feet before entering them. What matters is consistency, not the unit itself.
The shadow method can be surprisingly good on level ground with clean shadows, but it should not be treated as survey-grade measurement. Its accuracy depends on the tree being upright, the ground being reasonably flat, the tree top casting the shadow tip you measure, and your reference shadow being marked correctly. Any one of those assumptions can push the estimate high or low.
Professional tree height methods handle some of these problems differently. Oregon State University Extension describes a clinometer as a hand-held tool that measures vertical angles such as slope, road grade, and tree height, and notes that a percent scale can be used from a measured distance to measure heights. A clinometer still needs practice, but it is better suited than shadows when the sun is unavailable or the shadow does not fall on open ground.
For high-accuracy tree records, shadow methods are usually not the preferred approach. American Forests’ tree-measuring guidelines describe the sine method with laser rangefinder and clinometer readings as a direct method for measuring tree height from the ground when the top and base can be seen with a laser. That level of method is beyond what most homeowners need, but it explains why serious tree measurement is more involved than a single shadow.
The most common error is measuring the wrong shadow tip. A tall tree’s highest point may be a small twig that casts a faint tip, while a lower branch casts a stronger, easier-to-see outline. If you measure the lower branch shadow, the calculator underestimates the tree.
The second error is mixing sloped and level distances. If the tree stands uphill from the shadow tip, or if the shadow runs down a slope, the ground measurement is no longer the same kind of horizontal distance used in the simple triangle. The calculator has no slope correction, so the result may look clean while the geometry underneath is compromised.
The third error is measuring at different times. Even a short delay matters when the sun is low and shadows are changing quickly. Mark first, measure second. If a breeze is moving branches, wait for a steadier moment and average several reasonable readings rather than trusting one flickering shadow edge.
Slopes are the biggest field limitation for the shadow method. A flat driveway beside a sloped yard can sometimes help if both the reference shadow and tree shadow land on the same plane, but that is not always possible. If the tree base, your feet, and both shadow tips are on noticeably different elevations, switch to a clinometer, rangefinder, or professional measurement.
Leaning trees create a different problem. Tree height is normally the vertical distance from the base plane to the top, not the length of the leaning trunk. American Forests describes tree height as the vertical distance between an upper plane touching the tip and a lower plane through the base vertical distance. A leaning trunk can cast a shadow that represents horizontal offset as well as height, so a simple base-to-shadow-tip measurement can mislead you.
Broad crowns add uncertainty because the highest point may not be visually obvious. Older open-grown trees can have uneven crowns with several competing tops. If the goal is a casual estimate, a careful shadow reading is fine. If the goal is a champion-tree nomination, insurance record, arborist report, or construction clearance, use a more rigorous method.
A shadow estimate is usually enough when you are making low-stakes comparisons. It can tell you whether a tree is closer to 25 feet or 60 feet, whether it has outgrown a small ornamental category, or whether a removal-cost calculator should be run with the small, medium, or large height band. For those uses, the method’s speed is its main advantage.
It is also useful for teaching geometry in a way that feels concrete. Students can see that the same proportion works for a person, a pole, and a tree, then test how timing and measurement quality affect the result. Utah State University Extension’s tree-height activity uses a stick, arm length, and sight line to project a right triangle for measuring tall trees by projecting a right triangle, which is the same field-measurement family as the shadow calculator.
For garden planning, the estimate can help you think ahead. A 15-foot young tree planted near a roofline is a different decision from a 45-foot tree with a spreading crown. Height does not tell the whole story, but it starts the conversation before canopy spread, root space, pruning access, and species behavior are considered.
Use a clinometer or laser-based method when the tree shadow is blocked, the ground is sloped, the tree is leaning, or the number matters for money or safety. A contractor, consulting forester, or certified arborist may use more than one measurement position because the visible top from one angle may not be the true top. That extra care matters when height affects fall radius, rigging, timber volume, or formal records.
Use the stick method when you have no clean shadow but can see the full tree from the side. The stick method is still geometry, but it compares your line of sight to a vertical stick rather than comparing shadow lengths. It has its own assumptions: the base and top must be visible, the stick must stay vertical, and your sight line to the base should be close to horizontal.
Use professional help when the tree may fail, interfere with utilities, require climbing, or affect a structure. A height estimate does not reveal internal decay, root damage, included bark, weak attachments, soil failure, or the load on a limb. If the tree is a hazard question, height is only one detail in a much larger inspection.
Tree height becomes more useful when paired with diameter. A tall, skinny young tree and a tall, large-diameter mature tree can have very different value, risk, and work requirements. Use the /tools/tree-diameter-calculator/ if you need DBH context, then use the /tools/dbh-basal-area-calculator/ when you are thinking about stand density rather than one tree.
Height also affects removal and pruning planning, but not by itself. Access, nearby targets, species, trunk diameter, crown spread, deadwood, slope, and equipment needs can matter as much as height. If the calculator tells you a tree is taller than expected, use that as a prompt to gather better information before relying on the /tools/tree-removal-cost-calculator/ or /tools/tree-trimming-cost-calculator/.
For wood, heat, or volume planning, height must be narrowed to the useful part of the tree. Total height is not the same as merchantable height, log length, or firewood volume. If the tree will become fuel, the /tools/firewood-cord-calculator/ and /tools/firewood-btu-calculator/ are more relevant after the tree is cut and stacked.
Write down the date, time, weather, your height, your shadow length, the tree shadow length, and a short note about the site. A note such as “clear sun, shadow crossed level lawn, tip slightly fuzzy” is more useful than a number alone. If you repeat the measurement later, you can tell whether the difference is tree growth or field noise.
Take two or three readings from the same session if the shadow tip is hard to mark. You can average close readings, but do not average a clean reading with an obviously bad one. If one value is far away from the others, check for a measurement mistake before treating the average as better.
For long-term tracking, measure in similar seasonal conditions when possible. A leafless deciduous tree may have a different visible shadow tip than the same tree in full leaf. The tree did not suddenly shrink or grow; the shadow outline changed. Record enough context that the next measurement makes sense.
Round the calculator’s result to match the quality of the fieldwork. If your tree shadow is measured to the nearest foot, reporting 52.384 feet is misleading. A practical result would be “about 52 feet” or “roughly 50 to 55 feet,” depending on how clean the site was.
Think in bands when the next decision is not sensitive to one or two feet. For many home uses, the difference between 43 and 45 feet does not change the plan. The difference between 25 and 60 feet does. Use the calculator to get the scale right, then decide whether the decision deserves a better method.
If the result surprises you, rerun the measurement before acting. Measure your shadow again, recheck the tree shadow, and look for slope or crown issues. A surprising result can be correct, especially with tall trees, but it should earn your trust through repeatable measurements.
Do not climb a tree, stand in traffic, step onto a roof, cross a fence, or enter a utility corridor to get a better shadow measurement. The whole point of the shadow method is to stay on the ground and avoid unnecessary risk. If the shadow tip falls somewhere unsafe, choose another time, another viewpoint, or another method.
Do not use this calculator to decide whether a tree can hit a house, power line, vehicle, or neighbor’s property. A tree’s fall path depends on lean, canopy weight, defects, wind, roots, terrain, and failure mode. Height can inform the question, but it cannot answer the risk question alone.
For any tree near conductors, call the utility or a qualified tree professional rather than measuring close to the line. For a tree with cracks, heaving soil, fresh lean, hanging limbs, or large dead sections, keep distance and get a professional assessment. The calculator can wait; site safety comes first.
The Tree Height Calculator is best used as a clear, repeatable shadow-method estimate. Measure your height, your shadow, and the tree’s shadow at the same time; keep the units consistent; and use the result as an honest planning number rather than a perfect measurement.
The result is strongest on level ground with direct sun, a visible shadow tip, and an upright tree. It gets weaker on slopes, in broken shade, around leaning trunks, and under broad irregular crowns. When the number affects safety, money, formal records, or professional work, use it as a starting point and move to a clinometer, laser method, arborist, or forester before making the final call.
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Tree height = (Your height / Your shadow length) x Tree shadow length. All measurements should be in the same unit. The result assumes a level surface, a single straight tree, and a clear sun shadow for both you and the tree. On a slope, accuracy drops. The method fails in early morning or late afternoon when shadows are very long. For most accurate results, take measurements within 10 minutes of solar noon, when the sun is highest and shadows are shortest.
The long-form review for this page covers Tree Height Calculator. Its bottom source list includes 6 external citations pulled from the long-form guide, then deduplicated with the tool’s frontmatter sources.
The shadow method is the classic: on a sunny day, measure the length of the tree’s shadow, then measure your own shadow and your own height at the same moment. Because the sun’s angle is the same for you and the tree, the ratio of heights equals the ratio of shadow lengths. So tree height = (your height / your shadow) x tree’s shadow. A 6-foot person with a 10-foot shadow measuring a 75-foot tree shadow gives a tree height of 45 feet.
On level ground with the sun overhead, the shadow method is accurate to within 5 percent. On a slope, accuracy drops because the tree’s shadow length is harder to measure accurately. The biggest error source is partial shadow - if the tree’s shadow ends in dappled light under another tree, you will under-measure the shadow. The method also fails in early morning or late afternoon when shadows are very long and the sun’s angle is shallow.
The most common alternatives are: (1) the clinometer or hypsometer - a sighting instrument that reads percent slope, used by foresters; (2) the smartphone app - many forestry and arborist apps use the camera and accelerometer to measure height directly; (3) the stick method - drive a stick into the ground at a known distance, sight along the stick to the top of the tree, and use similar triangles; (4) the laser rangefinder - some models have a built-in height calculation that needs the distance to the tree and the angle to the top.
The sun’s rays are essentially parallel over the scale of a person and a tree, so any two vertical objects at the same place and time cast shadows that are proportional to their heights. This is the same principle as similar triangles in geometry - a tall object and a short object side by side cast shadows whose lengths are in the same ratio as their heights, regardless of the actual sun angle. The method works at any time of day when the sun is casting a shadow (sun altitude above about 15 degrees).
No, the shadow method requires direct sun to cast a shadow. On a cloudy day, the alternatives are: a clinometer (most accurate, $30 to $80 for a basic one), a smartphone app (less accurate but accessible), or the stick method. The stick method is the best free option: stick a 3-foot stick in the ground at a measured distance from the tree, walk back until you can sight the top of the stick aligned with the top of the tree, then use similar triangles to compute the height.
The tallest trees in North America are the Pacific Coast redwoods (Sequoia sempervirens), reaching 350+ feet. The tallest hardwood is the coast Douglas-fir, at 300+ feet. Among common yard trees: oaks reach 60 to 80 feet, maples 50 to 80 feet, sweetgum 60 to 75 feet, sycamore 75 to 100 feet, tulip poplar 100+ feet. Small ornamental trees (dogwood, redbud, Japanese maple) typically max out at 20 to 30 feet.
Yes, for sawlog trees, height determines the merchantable trunk length - the straight, clear portion above the stump and below the first major limb. A 20-inch DBH oak with 2 logs (32 feet) of merchantable height is worth significantly more than the same oak with only 1 log (16 feet). Foresters price sawlogs by the board foot, scaled to the merchantable height. For veneer-quality trees, straight height is even more critical - a 50-foot clear bole is worth far more than a 25-foot bole of the same diameter.