Tree Carbon Offset Calculator
Find how many trees it takes to offset a given amount of CO2 per year, assuming about 21 kg absorbed per tree annually.
This assumes a mature tree absorbs roughly 21 kg of CO₂ each year. Young trees pull down far less, and species, climate, and lifespan all matter, so treat the count as a planting target rather than a precise guarantee.
How it works
Growing trees pull carbon dioxide out of the air and lock it into wood and roots. A common planning figure is that a mature tree absorbs around 21 kilograms of CO₂ per year, so offsetting your emissions is a matter of division.
Enter how much CO₂ you want to cancel out — in tonnes or kilograms — and the calculator divides by 21 kg per tree, then rounds up, since you can't plant a fraction of a tree.
Pair it with the carbon footprint calculator to close the loop: estimate your yearly emissions there, then bring the tonnes here to see roughly how large a planting effort it would take to balance them.
Frequently asked questions
Is 21 kg per tree per year accurate?
It's a reasonable mid-range figure for a mature tree, but real absorption swings widely with species, age, climate, and health. Young saplings capture far less at first and only reach full stride after years of growth.
Do trees really offset emissions permanently?
Only while the carbon stays stored. If a tree burns, decays, or is cut and not replaced, much of its captured carbon returns to the atmosphere. Reliable offsets depend on forests being protected over the long term.
Should I plant trees instead of cutting emissions?
Planting helps, but it works best alongside reducing emissions, not instead of it. Trees take years to reach full absorption and there's limited land, so trimming your footprint first and offsetting the rest is the stronger approach.