About the Tree Carbon Sequestration Calculator
This tree carbon sequestration calculator estimates how much carbon dioxide a living tree has removed from the air and locked into its wood. Measure the trunk at breast height (4.5 ft or 1.37 m above the ground) — either the diameter or the circumference with a tape — choose the species group, and the calculator estimates the tree’s dry biomass, the carbon it contains and the equivalent CO₂.
It uses the national-scale biomass equations published by USDA Forest Service scientists Jenkins, Chojnacky, Heath and Birdsey (2003), which predict total above-ground dry biomass from diameter for ten US species groups, plus their coarse-root ratios for hardwoods and softwoods. They were the basis of US national forest carbon reporting for many years and remain widely used for individual-tree estimates. Height is not needed: across thousands of trees, diameter alone predicts biomass well, and the species group captures differences in wood density and form.
Dry wood is about half carbon, and each kilogram of carbon corresponds to 44/12 ≈ 3.67 kg of CO₂. Dividing by the tree’s age gives its average yearly uptake, though real trees sequester slowly when young, fastest in mid-life and slowly again when old. In the source data, 80% of trees fell within roughly 20–35% of their group equation, so treat any single-tree result as an estimate; open-grown urban trees with wide crowns may differ more.
With the default inputs, the co₂ stored is 2,402 kg. Change any value above to recalculate instantly.
How to use the tree carbon sequestration calculator
- 1Measure the trunk 4.5 ft (1.37 m) above the ground — diameter, or circumference with a tape.
- 2Choose whether you measured diameter or circumference and the unit.
- 3Pick the species group closest to your tree.
- 4Enter the tree’s approximate age and how many similar trees you have.
- 5Read the CO₂ stored and the average yearly uptake.
Formula and method
DBH is the trunk diameter in centimetres at breast height (circumference ÷ π if you measured around the trunk). Above-ground dry biomass AGB in kilograms comes from the Jenkins et al. (2003) equation for the chosen species group, using its β₀ and β₁ coefficients. Coarse-root biomass is estimated as a ratio of AGB that depends on diameter, with separate coefficients for hardwoods (r₀ = −1.6911, r₁ = 0.8160) and softwoods (r₀ = −1.5619, r₁ = 0.6614).
Total dry biomass is multiplied by the carbon fraction CF (50% by default) to get carbon, and by 44/12, the ratio of the molecular mass of CO₂ to that of carbon, to express it as CO₂. The average yearly figure simply divides the stored CO₂ by the tree’s age. Fine roots, leaves shed over the years and soil carbon are not counted.
- DBH
- Diameter at breast height (cm)
- β₀, β₁
- Species-group biomass coefficients (Jenkins et al. 2003, Table 4)
- r₀, r₁
- Coarse-root ratio coefficients (Table 6)
- CF
- Carbon fraction of dry biomass
Worked examples
16-inch oak
A 16-inch (40.6 cm) oak has about exp(−2.0127 + 2.4342 × ln 40.64) ≈ 1,103 kg of above-ground dry biomass and about 207 kg of coarse roots. Half of the 1,310 kg is carbon (655 kg), equal to about 2,402 kg of CO₂ — roughly 60 kg a year over 40 years.
30 cm pine, 25 years old
A 30 cm pine has about 313 kg of above-ground biomass and 67 kg of coarse roots. That holds about 190 kg of carbon, or roughly 697 kg of CO₂ — about 28 kg a year over 25 years.
Douglas-fir measured by circumference
A 60-inch circumference is a diameter of 60 ÷ π ≈ 19.1 inches, or 48.5 cm. The Douglas-fir equation gives about 1,415 kg of above-ground biomass plus about 301 kg of roots, storing about 3.1 tonnes of CO₂.
Ten young cottonwoods, trunks only above ground
Each 20 cm cottonwood has about 140 kg of above-ground biomass. Ten such trees hold about 699 kg of carbon, or 2,564 kg of CO₂, an average of about 171 kg of CO₂ a year for the group over 15 years.
Frequently asked questions
How much CO₂ does a tree absorb per year?+
It varies enormously with species, size and growing conditions. A young tree may absorb only a few kilograms a year, while a large, healthy mid-life hardwood can add tens of kilograms of CO₂ a year. Dividing the CO₂ stored by the tree’s age, as this calculator does, gives a lifetime average.
How do I measure diameter at breast height?+
Measure 4.5 feet (1.37 m) above the ground on the uphill side of the trunk. Wrap a tape around the trunk to get the circumference and divide by π (3.1416), or use a diameter tape. If the trunk forks below breast height, measure each stem and treat them as separate trees.
Why does the calculator not need tree height?+
The USDA Forest Service equations used here were fitted to diameter alone because diameter is measured on every inventory tree and predicts biomass well. Height adds some accuracy for unusual trees, but the published diameter-only fits for the ten species groups have R² values between 0.94 and 0.99.
How many trees offset one tonne of CO₂?+
By these equations, a tonne of CO₂ is roughly what is stored in a single 11-inch oak or maple, including roots, but that took decades to accumulate. On a yearly basis, offsetting one tonne a year would need dozens of mid-sized trees growing steadily, which is why tree planting works best alongside cutting emissions.
What happens to the carbon when a tree dies?+
As dead wood decomposes or burns, most of its carbon returns to the atmosphere as CO₂. Carbon stays locked away longer if the wood becomes long-lived products like timber framing or furniture, or is buried in waterlogged soils where decay is slow.