How much CO2 does one tree absorb?

It varies hugely by species, age, climate, and management, but a common planning figure is around 21 kg CO2 per mature tree per year, or roughly 0.5 to 1 tonne over a 40-year life. Young trees absorb little; the peak comes in their middle decades.

Why does the timeframe matter?

Trees absorb carbon gradually over decades, not instantly. Spreading the same emissions over 10 years needs more trees than over 40 years, because each tree has fewer years to do its work in the shorter window.

Is planting trees a valid offset?

Tree planting can help but is not a like-for-like cancellation of fossil emissions. Carbon stored in trees can be released by fire, disease, or felling, and the absorption takes decades. Reducing emissions at source is always the priority.

Which species absorbs the most?

Fast-growing broadleaf species like oak and beech in temperate climates, and many tropical species, sequester more per tree than slow conifers or small ornamentals. The tool uses representative average rates, so treat the species choice as indicative.

Should I use this for compliance claims?

No. It is a communication aid to make a CO2e figure tangible. Verified offsetting requires accredited projects with measured, additional, and permanent sequestration — not a back-of-envelope tree count.

Tree Equivalent Carbon Calculator

This calculator turns an abstract CO2e figure into a relatable number of trees. You enter the emissions, pick a species and a timeframe, and it works out how many trees would be needed to absorb that carbon over the period you choose, using average sequestration rates.

How it works

Each species has an average annual absorption rate. Over your chosen number of years, one tree absorbs that rate multiplied by the years, and the tree count is simply the total CO2e divided by per-tree lifetime absorption:

co2_kg          = amount in kg (tonnes × 1000 if needed)
per_tree_total  = species rate (kg CO2/yr) × years
trees_needed    = co2_kg / per_tree_total   (rounded up)

A widely used planning rate is around 21 kg CO2 per tree per year for a mature broadleaf, but young trees absorb far less, so these figures describe averaged lifetime performance rather than a sapling’s first year.

Tips and example

One tonne of CO2e (1,000 kg), spread over 40 years using a 21 kg/yr rate, needs about 2 trees — because each tree absorbs roughly 840 kg over that period. Halve the timeframe to 20 years and you need about 3 trees for the same emissions. Use the result to communicate scale, but remember that avoiding the emission in the first place is always more reliable than planting to compensate for it.