Big-tree measurer

Champion-tree registers rank big trees by one sum: inches around the trunk, plus feet of height, plus a quarter of the crown's average spread. Enter the trunk's circumference at 4.5 feet or its diameter, the height, the widest crown spread and the spread at right angles to it. The measurer gives the diameter at breast height, the three parts of the score with the total points, and where to nominate a tree that might rank. Choosing one of the trees and shrubs we grow adds its page and the mature height it gives. The points compare trees of one species and say nothing about a tree's age. Every rule is shown with its source, beginning with American Forests' handbook for measuring champion trees.

How the trunk was measured The registers count inches around. A diameter from calipers or a diameter tape is turned into inches around, times 3.1416. Trunk circumference in inches Wrap the tape around the trunk 4.5 feet above the ground. On a slope, measure the 4.5 feet up from halfway between where the trunk meets the ground uphill and downhill. Each inch around is a point. Height in feet From the highest twig straight down to the ground, not along the trunk. A laser rangefinder and a clinometer, by the sine method, read it best, and a phone or a stick gives a first estimate. How to measure height. Widest crown spread in feet Find the two branch tips farthest apart, mark the ground under each, and pace or tape between the marks. The line need not pass through the trunk. Spread at right angles in feet Turn a quarter turn from the first line and measure the widest spread that way. The two are averaged, and a quarter of the average counts. Species, if you know it It changes no figure. A species we grow adds its page and the mature height the page gives, and an empty box means another tree. All 364 trees and shrubs we grow are in the list.

Numbers update as you type.

The measurer needs JavaScript. These are its rules. American Forests' Champion Trees Measuring Guidelines Handbook scores a tree as "Trunk Circumference (inches) + Height (feet) + 1/4 Average Crown Spread (feet) = Total Points". The National Champion Tree Program, run by the University of Tennessee, Knoxville since 2024, uses the same sum. The diameter at breast height is the circumference divided by pi, 3.1416, and a diameter times pi gives the inches around. The average crown spread is the mean of the widest spread and the widest spread at right angles to it, and a quarter of it counts. The total is rounded to the nearest point, as the 2024 national register prints most of its trees. Under 100 points, two trees within 3 points of each other are co-champions, and from 100 points, trees within 3 percent of the larger tree's total. The tape goes around the trunk 4.5 feet above the ground, and on a slope 4.5 feet above the middle of the slope. On a leaning trunk it goes at right angles to the lean. Where a burl or a limb swells the trunk at 4.5 feet, the narrowest point between there and the ground is measured. Where one tree forks below 4.5 feet, the national program takes the narrowest waist below the fork, or the functional circumference if that is smaller. The functional circumference is the square root of the sum of each stem's circumference squared. The height runs from the highest twig straight down to the ground at mid-slope, best read by the sine method with a laser rangefinder. The measurer refuses a trunk over 1,200 inches around, a height over 400 feet or a crown spread over 300 feet. The national program and each state's big-tree program take nominations on forms of their own. The points compare trees of one species and say nothing about a tree's age.

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How to measure a big tree

Wrap the tape 4.5 feet up. American Forests' handbook wraps it "at 4.5 feet above mid-slope of the tree's base". On a slope, the 4.5 feet start halfway between where the trunk meets the ground uphill and where it meets it downhill.
Square it to a lean. On a leaning trunk the handbook wraps the tape "at 90 degrees to the axis of the lean, instead of parallel to the ground."
Go under a swelling. Where a burl, a knot or a low limb swells the trunk at 4.5 feet, the handbook takes "the smallest circumference between 4.5 feet and the ground."
Measure a low fork twice. Where one tree forks below 4.5 feet, the National Champion Tree Program takes the narrowest waist below the split and the functional circumference, and keeps the smaller. The functional circumference is the square root of the sum of each stem's circumference squared.
Two trees grown together are two trees. The handbook follows the pith, the center of each trunk, down to the ground: "If the pith lines at ground level are separated, we have more than one tree." Only the largest trunk is measured then.
Read the height to the highest twig. The national program measures height "from the highest point on the tree straight down to the ground", not along the trunk.
Sight from under the top. With a clinometer or a phone, the handbook takes the level distance to the spot beneath the top, since "The highest twig of a tree is often not directly over its base." A laser rangefinder and the sine method remove that error.
Average two crown spreads. American Forests' handbook takes the widest spread from branch tip to branch tip over the ground, then the widest spread at right angles to it, and averages the two. Pace or tape each, and a quarter of the average counts.
A worked example. A tree 200 inches around at 4.5 feet, 90 feet tall, with crown spreads of 100 and 80 feet, scores 200 + 90 + 90 ÷ 4 = 312.5, or 313 points. Its diameter at breast height is 200 ÷ 3.1416 = 63.7 inches.
Nominate it. The National Champion Tree Program takes nominations from the public, with six photographs of the tree. Each state keeps its own big-tree program with its own form, such as New York's Big Tree Register and North Carolina's Champion Tree Program.

The score and the measuring rules follow American Forests' Champion Trees Measuring Guidelines Handbook of 2014, by Robert Leverett and Don Bertolette. Its formula is "Trunk Circumference (inches) + Height (feet) + 1/4 Average Crown Spread (feet) = Total Points". American Forests kept the national register from 1940, and in 2024 the program moved to the University of Tennessee, Knoxville. The National Champion Tree Program's measuring page gives the same sum and names the handbook as its reference. New York's register and North Carolina's program score trees by the same formula.

The sources disagree on where the tape goes. The handbook measures 4.5 feet above mid-slope, "where we judge the seed to have fallen", and notes that "the forestry profession typically goes 4.5 feet above the upslope point." North Carolina's basic measuring guidelines measure from the uphill side, 4.5 feet along the stem of a leaning tree, and 1.5 feet above the swell of a buttressed cypress or tupelo. Where a tree forks below 4.5 feet, North Carolina measures the larger stem at 4.5 feet. The measurer follows the national program and the handbook, since the national register's points are measured their way. For a state's own register, the state's guide comes first.

The handbook's glossary finds the diameter at breast height by "dividing CBH by the constant pi", CBH being the circumference at breast height. The 2024 register lists almost every diameter that way. For the crown, its quickest method is "to take two measurements of the widest spreads at 90 degrees to one another", averaged. It adds that "the widest spread does not have to go through the trunk." The national program recommends several measurements of the spread, and North Carolina's guide takes the widest and the narrowest. The national program's page sets no rounding. Its 2024 register prints whole points, rounded to the nearest point for most of its 547 trees, and the measurer does the same. The handbook's examples round the crown's quarter down instead, and North Carolina rounds each part to the nearest whole number before adding, so a state's total can differ by a point.

The national program names co-champions "within 3 points of each other" when the larger tree has under 100 points, and "within 3% of the larger tree's total points" from 100 points. New York's register sets the same band, and North Carolina names co-champions within 10 points. The handbook calls the sine method "the simplest and most direct way to measure tree height from the ground when the top and base can be seen by the infrared laser". The national program accepts estimates by the stick method from the public, and asks which method was used. The measurer's limits sit above the largest trees on the 2024 register: a giant sequoia 1,026.6 inches around, a coast redwood 321 feet tall and a live oak whose crown spreads 161 feet.

The points are a sum for comparing trees of one species, not a measure of a tree's age or worth. Size is a poor clock, as How old is that tree, really? explains, and Why almost every tree height you read is too tall covers measuring height honestly. For a tree you plant, the growth estimator shows how its height and trunk grow, and the planting-site check says whether it will thrive where it goes. Questions the page leaves open can go to us through the support page.