How this instrument works
'A tree absorbs X amount of CO2' sounds like it should have one clean answer, but it doesn't — even the EPA, whose own Greenhouse Gas Equivalencies Calculator this tool is built on, publishes two structurally different sequestration figures depending on what you're actually asking about. One figure describes a single urban tree growing in a yard or street planting; the other describes an acre of established forest, which holds dozens of trees plus understory vegetation and soil carbon dynamics a lone urban tree doesn't have. These are not two ways of stating the same fact — they're answers to two different questions.
That's why this calculator asks you to pick a scope first: urban tree or forest acre. The urban-tree figure, 0.060 metric tons of CO2 per tree per year, comes from EPA's use of McPherson, van Doorn & Peper's 2016 urban tree growth and allometric research for the USDA Forest Service, averaged across a tree's growth from planting through maturity. The forest-acre figure, 1.00 metric ton of CO2 per acre per year, comes from EPA's 2024 GHG Inventory, using USDA Forest Service Forest Inventory and Analysis (FIA) data on established U.S. forest carbon uptake. Selecting a scope multiplies that scope's factor by your quantity and number of years — nothing more.
The one rule this calculator enforces by design: the two scopes are never added together or blended into a single combined number. Ten urban trees are not '10% of a forest acre,' and a forest acre's per-acre sequestration rate says nothing about any individual tree within it. If your question is about street trees or a yard planting, use the urban-tree scope; if it's about a tract of forest land, use the forest-acre scope — and if you need both, run the calculator twice and keep the two results clearly separate rather than summing them.
- Choose a scope: urban tree (per individual tree) or forest acre (per acre of established forest).
- Enter the quantity — number of trees if you picked urban tree, or number of acres if you picked forest acre.
- Enter the number of years you want to project the absorption over.
- Read the total CO2 absorbed, in metric tons, for that scope, quantity and time period.
- Never add an urban-tree result to a forest-acre result — they're two distinct EPA equivalency figures, not interchangeable units.
Worked example — 10 urban trees versus 10 forest acres, 5 years
Ten newly planted street trees, tracked over 5 years under the urban-tree scope: 0.060 × 10 × 5 = 3.0 metric tons of CO2 absorbed. That's the EPA's per-urban-tree equivalency figure applied to a quantity of individual trees.
Now switch the scope to forest acre and enter the same quantity and years, 10 and 5: 1.00 × 10 × 5 = 50.0 metric tons of CO2 — over 16 times higher than the urban-tree result for the same '10' and '5.' That gap is not a mistake to reconcile; it's the whole point of keeping the scopes separate. Ten individual trees and ten acres of forest are simply not comparable quantities, and this calculator's job is to never pretend otherwise by blending them into one number.
Questions
Why doesn't this calculator just give one CO2-per-tree number?
Because there isn't a single honest one to give. EPA's own Greenhouse Gas Equivalencies methodology publishes a per-urban-tree figure and a per-forest-acre figure that measure genuinely different things — an individual tree's growth versus an acre of established forest's combined tree, understory and soil carbon dynamics — and averaging or blending them would misrepresent both. This calculator keeps them as two separate, selectable scopes instead of manufacturing a false single answer.
Can I add together an urban-tree result and a forest-acre result?
No — don't sum them. A quantity of individual urban trees and a quantity of forest acres are not the same kind of unit, and combining their CO2 totals would produce a number that doesn't correspond to anything real. If you need to describe both a street-tree planting and a forest tract, report the two results separately and label which scope each one uses.
Where does the urban-tree factor of 0.060 metric tons CO2 per year come from?
It's EPA's Greenhouse Gas Equivalencies Calculator figure, built on urban tree growth and allometric equations published by McPherson, van Doorn & Peper (2016) for the USDA Forest Service's Pacific Southwest Research Station. It represents an average annual sequestration rate for an urban tree across its growth from planting to maturity, not a fixed rate that applies identically in every year of a tree's life.
Where does the forest-acre factor of 1.00 metric ton CO2 per year come from?
It's drawn from EPA's 2024 Greenhouse Gas Inventory, Chapter 6 (Land Use, Land-Use Change and Forestry), which itself is based on USDA Forest Service Forest Inventory and Analysis (FIA) data measuring carbon accumulation across established U.S. forest land. It's an average per-acre annual rate for existing forest, not a projection specific to newly planted or regenerating forest.
Does either figure account for a tree or forest eventually releasing its carbon (through decay or fire)?
No. Both EPA figures represent annual sequestration — carbon actively being absorbed and stored — not a lifetime net accounting that subtracts eventual release through decomposition, wildfire, harvest or land-use change. Treat this calculator's output as an estimate of ongoing uptake over the years you specify, not a permanent, guaranteed carbon-storage total.