Choose how you want to enter your CO2 to offset, pick a tree species and a planting density, and get an order-of-magnitude estimate of how many trees and how much land it would take to compensate it.
Based on an average petrol or diesel car emitting about 0.17 kg of CO2 per km.
A tree absorbs CO2 gradually over its life, not all at once, so choose the number of years over which you want to spread the compensation.
This is a rough order-of-magnitude estimate, not a scientifically exact figure. Real CO2 absorption per tree varies a lot with species, soil, climate, and age, and a young tree absorbs far less than a mature one. Planting a tree does not compensate emissions instantly, the absorption is spread over decades, and reducing emissions at the source stays more important than offsetting them.
Why planting a tree today does not offset your emissions today
A newly planted sapling absorbs almost nothing in its first year. Carbon absorption builds up slowly as the tree grows, so the CO2 emitted by a flight or a year of driving is only fully offset once the trees planted for it have had years, sometimes decades, to grow. This calculator spreads the absorption over the compensation period you choose, so the trees and land figures reflect an average rate over that time, not an instant fix.
Absorption rates and planting densities used in this estimate
| Tree type | Approx. CO2/tree/year | Approx. maturity |
|---|---|---|
| Slow-growing broadleaf (oak, birch) | 10 kg | 40 years |
| Fast-growing conifer (Scots pine) | 20 kg | 25 years |
| Fast-growing tropical species | 30 kg | 15 years |
| Planting density | Approx. trees/hectare |
|---|---|
| Natural / sparse forest | 400 |
| Managed reforestation | 1200 |
| Dense plantation | 2500 |
Limits of this calculator
These figures are averages drawn from commonly cited ranges, not a scientific measurement of any specific forest. Fire, disease, drought, or logging can wipe out a stand of trees and cancel the compensation it was meant to provide, which is a real risk with any offset scheme based on new planting. Treat the trees and land figures here as an order of magnitude to help you understand the scale of an offset, and remember that cutting emissions at the source is always a more reliable step than compensating for them afterwards.
The Woodland Carbon Code and certified offset schemes
In the UK, the Woodland Carbon Code is the government-backed standard for verifying that a planting project actually removes the carbon it claims to, with independent validation and long-term monitoring built in, which is a stronger guarantee than an uncertified planting pledge. Species commonly planted under such schemes include oak, birch, and Scots pine, matching the growth types used in this tool. England's Trees Action Plan has also set targets to significantly expand woodland cover over the coming decades. For a broader view of your personal emissions before you look at offsetting them, see the Carbon Footprint Estimator or the Plastic Footprint Calculator.