Tree Carbon Sequestration Calculator
Trees remove carbon dioxide from the atmosphere through photosynthesis and store it as biomass in wood, bark, branches, and roots. The amount of CO2 sequestered each year depends on how fast the tree grows (annual biomass increment), the carbon fraction of that biomass (approximately 50 percent by dry weight), and the ratio of CO2 molecular weight to carbon (44/12 = 3.667). This calculator uses the USDA Forest Service method: CO2 sequestered per year = annual dry biomass growth (kg) x 0.50 (carbon fraction) x 3.667 (CO2/C ratio). Enter the annual biomass growth per tree and the number of trees to find total annual CO2 sequestration in kilograms.
Carbon sequestration formula
CO2 per tree (kg/yr) = Annual biomass growth (kg) x 0.50 x 3.667
Total CO2 (kg/yr) = CO2 per tree x Number of trees
Total CO2 (metric tons/yr) = Total CO2 / 1000
The carbon fraction of 0.50 (50 percent) is the standard value used by the USDA Forest Service and IPCC guidelines for temperate tree species. The conversion factor 3.667 is the ratio of CO2 molecular weight (44 g/mol) to carbon atomic weight (12 g/mol).
Understanding tree carbon sequestration
- Young, fast-growing trees generally sequester more carbon per year than old, slow-growing trees of the same species.
- A single mature oak tree may store over 1,000 kg of carbon in its total biomass, built up over decades.
- Forests also store carbon in soil, leaf litter, and root systems, which are not captured in above-ground biomass estimates alone.
- The USDA Forest Service estimates that US forests sequester about 750 million metric tons of CO2 per year, offsetting roughly 12 percent of total US greenhouse gas emissions.
- Planting trees is a long-term strategy. Most climate benefit builds over 10 to 40 years as trees reach maturity.
Frequently asked questions
How much CO2 does one tree sequester per year?
It varies widely by species, age, and growing conditions. A young urban tree typically sequesters 10 to 20 kg CO2 per year. A mature hardwood in a managed forest can sequester 20 to 50 kg CO2 or more per year. The USDA Forest Service iTree tools provide species-specific data.
What is the carbon fraction of biomass?
Approximately 50 percent of dry biomass is carbon, a value used across USDA and IPCC methodologies. This carbon is then converted to CO2 by multiplying by the molecular weight ratio 44/12 (approximately 3.667).
What does annual biomass growth mean?
Annual biomass growth is the mass of new wood, bark, and leaves added per tree per year, measured in kilograms of dry biomass. This can be estimated from diameter increment measurements or species-specific growth tables.
Does this calculator account for carbon already stored in the tree?
No. This calculator estimates annual CO2 sequestration from new growth only, not the total carbon stock already stored in the tree. To estimate total stock, multiply total biomass by 0.50 (carbon fraction) then by 3.667.
Where can I find reliable biomass growth data for my trees?
The USDA Forest Service iTree suite (itreetools.org) and the USDA Forest Products Laboratory provide species-specific biomass equations and growth data. Your state Cooperative Extension service also publishes regional tables.
Official sources
- USDA Forest Service: Carbon in Forests (Forest Products Lab).
- EPA: Greenhouse Gas Equivalencies Calculator.
- USDA Forest Service iTree: iTree Tools.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.