Tree Carbon Offset Calculator
Find how many trees it takes to offset a given amount of CO₂, based on the carbon a growing tree absorbs each year.
How it works
Trees = CO₂ to offset ÷ (CO₂ per tree per year × years)
A healthy tree pulls carbon from the air as it grows, storing it in wood and roots. A commonly cited figure is about 21 kg of CO₂ per tree per year, though it varies hugely with species, age and climate — a sapling absorbs little, a mature tree far more. Dividing the CO₂ you want to cancel by what one tree captures gives the count; spreading the offset over more years lets each tree do more work.
Worked example
To offset 4,000 kg of CO₂ in one year at 21 kg per tree, you need 4,000 ÷ 21 ≈ 191 trees. Allow the trees ten years and the same job needs only about 20.
Frequently asked questions
How much CO₂ does one tree really absorb?
Estimates range from about 10 kg to over 40 kg a year depending on species, age and growing conditions. The 21 kg default is a widely used average for a growing temperate tree; adjust it if you have a better local figure.
Does the tree store carbon forever?
Only while it lives and the wood persists. If a tree burns or decays, most of the stored carbon returns to the atmosphere, which is why permanence is a key issue for offset schemes.
Is planting trees enough to be carbon neutral?
It helps, but trees take decades to reach full absorption and land is limited. Cutting emissions at the source is more reliable than offsetting them after the fact.
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This calculator is for educational purposes. Double-check important results before acting on them.