Tree Diameter
Calculate tree diameter at breast height (DBH) from circumference using d = C / π. Free tree diameter calculator with bark thickness support for forestry and arboriculture.
About This Calculator
The Tree Diameter Calculator computes the diameter at breast height (DBH) of a tree from its circumference. DBH is the standard measurement used by arborists, foresters, and ecologists worldwide to estimate tree size, volume, growth rate, carbon storage, and commercial timber value. Whether you are a professional forester, a student, or a gardener, this tool helps you quickly convert your tape-measured circumference into the precise diameter.
Formula & Methodology
The calculator uses the fundamental circle geometry formula: d = C / π, where d is the diameter and C is the circumference measured at breast height. The optional bark thickness input allows you to calculate the diameter under-bark (DUB) — the diameter of the wood inside the bark — using the formula: DUB = DOB − (2 × bark thickness). This is useful for timber volume estimation and ecological studies that require inside-bark measurements.
Regional Notes
United States: DBH is measured at 4.5 feet (1.37 m) above ground. Use inches or feet for circumference. India: Forestry departments typically measure DBH at 1.37 m (4.5 ft) following the US standard. UK & Europe: DBH is measured at 1.3 m (4.27 ft) above ground. Australia, Canada, New Zealand: Measure at 1.3 m (4.27 ft), except New Zealand which uses 1.4 m (4.59 ft). Japan & Korea: Measure at 1.2 m (3.93 ft). Always measure on the uphill side when on a slope.
Frequently Asked Questions
How do you calculate tree diameter from circumference?
To calculate tree diameter at breast height (DBH), divide the circumference by pi (π ≈ 3.14159). The formula is: d = C / π. For example, a tree with a circumference of 100 cm has a diameter of approximately 31.83 cm.
What is DBH and how is it measured?
DBH stands for diameter at breast height, the standard way to measure tree trunk diameter. In the US, measure 4.5 feet above ground. In Australia, Canada, and Europe, measure at 1.3 meters. In Japan and Korea, measure at 1.2 meters. Wrap a tape measure around the trunk at that height to get the circumference.
How do you calculate diameter under-bark?
Diameter under-bark (DUB) is the diameter of the wood inside the bark. To calculate it, subtract twice the average bark thickness from the diameter over-bark: DUB = DOB - (2 × bark thickness). Enter your bark thickness in our calculator to see both diameters.
How do I measure tree diameter on a slope?
On a slope, measure the circumference at breast height (typically 1.35 m or 4.5 ft) on the uphill side of the tree. Wrap the tape around the trunk at that height and divide by pi to get the diameter.
How do I find the diameter of a multi-stemmed tree?
For multi-stemmed trees, treat each stem separately if they originate below ground. Measure the circumference of the six largest stems, calculate each diameter, square each diameter, sum the squares, and take the square root of the total to get the overall tree diameter.
How much does a tree grow in diameter per year?
Most trees grow between 0.2 cm and 0.4 cm in diameter and between 1.5 cm and 2.5 cm in circumference per year. Growth rate varies by species, age, soil quality, and environmental conditions.
Can I use this calculator for leaning trees?
Yes. For a leaning tree on level ground, wrap the measuring tape around the underside face of the trunk at breast height (about 1.35 m from ground). Then divide the measured circumference by pi to find the diameter.
Is the tree diameter used for anything besides measurement?
Yes, DBH is used to estimate tree volume, biomass, carbon storage, growth rate, fertilizer requirements, and commercial timber value. It is a fundamental measurement in forestry, arboriculture, and ecological research worldwide.