Carbon Offset Calculator
Offsetting carbon emissions means paying for reductions or removals elsewhere to balance your own footprint. Two numbers matter: how much it costs, and what it represents in real terms such as trees planted. Because offset prices and tree sequestration rates vary enormously between projects, this calculator never assumes them. You enter your annual emissions in tonnes of CO2 equivalent, the price per tonne, and a per-tree absorption rate from a credible source, and it returns the total offset cost, the monthly cost, and the equivalent number of trees absorbing carbon for a year.
Carbon offset formula
Total cost = emissions (tonnes) * price per tonne
Monthly cost = total cost / 12
Emissions (kg) = emissions (tonnes) * 1,000
Equivalent trees = emissions (kg) / sequestration rate (kg per tree per year)
The cost is a simple product of emissions and price. The tree equivalence converts your emissions to kilograms and divides by the per-tree absorption rate you provide, giving the number of trees that would sequester that carbon in one year.
Carbon context
- Emissions are denominated in tonnes of CO2 equivalent so different greenhouse gases can be compared.
- Offset prices vary by project type and quality; use a figure from a credible marketplace or registry.
- Tree sequestration rates depend on species, age, climate, and management, so enter a sourced value.
- Offsets do not reduce your own emissions; guidance favours reducing first and offsetting the remainder.
- One tonne equals 1,000 kilograms, the conversion used between the cost and tree calculations.
Carbon offset: frequently asked questions
How is the cost of a carbon offset calculated?
The cost equals the tonnes of carbon dioxide you want to offset multiplied by the price per tonne. Offset prices vary widely by project type, quality, and market, so this calculator uses the price per tonne you enter rather than assuming a figure, then multiplies it by your emissions.
How many trees does it take to offset a tonne of CO2?
It depends entirely on the tree species, age, climate, and management, so there is no single number. The calculator asks you to enter a sequestration rate in kilograms of carbon dioxide absorbed per tree per year, taken from a credible source for your project, then divides your emissions by it.
Why are the rates and prices editable rather than fixed?
Carbon offset prices and tree sequestration rates differ enormously between projects and change over time. Presenting any single figure as fact would mislead. We follow a strict sourcing rule, so you supply the price per tonne and the per-tree absorption rate from a credible source, and the calculator does the arithmetic.
What is a tonne of CO2 equivalent?
A tonne of carbon dioxide equivalent (CO2e) expresses the warming effect of a quantity of greenhouse gases as the amount of carbon dioxide that would have the same impact. Emissions inventories and offsets are usually denominated in tonnes of CO2e so different gases can be compared on one scale.
Do offsets reduce my own emissions?
No. An offset funds emission reductions or removals elsewhere to compensate for your emissions; it does not reduce what you emit. Most guidance recommends reducing your own emissions first and using high-quality offsets only for the remainder that you cannot yet eliminate.
Official sources
- U.S. Environmental Protection Agency: Greenhouse Gas Equivalencies references.
- U.S. EPA: Global Warming Potentials and CO2 equivalents.
Reviewed by the CalculatorHub team, edited by James Graham, 16 June 2026. See our methodology.