Trees to Offset CO₂ Calculator
By Santaji GadepatilinUpdated October 27, 2026
Trees absorb carbon dioxide as they grow. Estimating how many trees would offset your emissions shows the scale of your footprint. This free trees to offset CO₂ calculator solves for whichever value you leave blank and shows the formula and steps.
How to use the trees to offset CO₂ calculator
Enter the CO₂ you want to offset each year and the CO₂ absorbed per tree. The number of mature trees needed is calculated.
Example
2 tonnes of CO₂ per year at 21 kg per tree → 96 trees.
The 21 kg figure is a rough average for a mature tree; fast-growing tropical trees can absorb more, and young trees much less.
CO₂ absorbed by trees
| Tree type and age | CO₂ per year (approx.) |
|---|---|
| Young tree (first 5–10 years) | 5–10 kg |
| Mature temperate tree | 10–25 kg |
| Fast-growing tropical tree | 20–50 kg |
| Hectare of growing forest | 5–20 tonnes |
Absorption varies widely with species, climate, soil and age. A commonly used average is about 20–25 kg per tree per year over its growing life.
Why trees are a slow fix
- Most CO₂ is absorbed as trees grow, over decades.
- Trees can die, burn or be cut, releasing their carbon.
- Planting the wrong species in the wrong place can harm ecosystems.
Trees are valuable for biodiversity, shade, soil and water, but they work best alongside cutting emissions, not as a replacement.
Land needed
At around 400–1,000 trees per hectare, offsetting 5 tonnes a year at 20 kg per tree needs 250 trees — roughly 0.25–0.6 hectares of land that stays forested.
Protecting existing forests
Keeping existing forests standing prevents large carbon releases and protects species. Protection is often more effective per unit of money than planting new trees.
Frequently asked questions
How much CO₂ does a tree absorb?
A commonly quoted average is about 21 kg per year for a mature tree, but it varies hugely with species, age, climate and soil.
Do newly planted trees absorb that much?
No. Young trees absorb much less; it can take decades to reach mature rates.
Is planting trees enough?
Trees help, but reducing emissions at the source is far more effective. Offsets work best as a complement.
How many trees offset 1 tonne of CO₂?
About 40–50 trees absorbing 20–25 kg each per year.
How much CO₂ does one tree absorb?
Typically 10–25 kg per year for a mature tree, depending on species and climate.