How the number of trees is worked out
A fully grown tree absorbs roughly 20 to 25 kg of carbon dioxide a year. This calculator uses 22 kg, a commonly used average, and you can change it.
A sapling absorbs much less at first. The calculator assumes its yearly uptake grows steadily until it is fully grown at about 20 years. That works out to about 60 kg in its first 10 years and about 230 kg in its first 20, close to the US EPA estimate for a newly planted tree.
So one tonne of CO₂ needs about 17 saplings growing for 10 years, about 5 growing for 20 years, or about 46 fully grown trees for a single year.
Why the first number can look huge
Results on the other calculators are often large: a house can be 200 tonnes or more of CO₂. Absorbing that in one year would take about 9,000 fully grown trees, which sounds impossible. But trees work over decades. The same 200 tonnes is absorbed by about 870 saplings planted now and grown for 20 years, or about 440 grown for 30 years, and those trees keep absorbing long after that.
Fast-growing native species suited to your area (bamboo, pongamia, some acacias) absorb more in their early years; slow, long-lived trees such as banyan and teak store more over their lifetime.
Everyday equivalents used
- Petrol car: 0.154 kg CO₂ per km, for a car doing 15 km a litre
- Home electricity: 71 kg CO₂ a month for a home using 100 units, at 0.71 kg per unit
- Saplings: one extra planted for every three, since young trees don't all survive
Frequently asked questions
How many trees offset a car or scooter?
A vehicle using 40 litres of petrol a month emits about 1.1 tonnes of CO₂ a year. One year of that is absorbed by about 5 saplings planted now and grown for 20 years.
Does planting trees cancel out my emissions?
Only partly, and slowly. Young trees absorb little for their first years, and trees can die or be cut down. Cutting fuel and electricity use first does more; trees are a good addition.
Which trees absorb the most carbon?
Large, long-lived native trees that grow well in your area usually store the most carbon over their lifetime. Ask your local forest department or a nursery what suits your soil and rainfall.
Sources
- US EPA Greenhouse Gas Equivalencies ↗ – CO₂ taken up by trees