🌍 Environment

Carbon Offset Calculator

Estimate a year of household emissions from electricity, gas, driving and flights, then see the offset cost and tree-years. Press Convert.

Written and reviewed by SM Arijul Islam · Last reviewed 28 October 2026 · Editorial standards · Report an error

About the Carbon Offset Calculator

A carbon offset is a payment for a reduction or removal elsewhere, measured in tonnes of carbon dioxide equivalent (tCO₂e). The first step is estimating your own emissions. This calculator uses average factors: about 0.386 kg CO₂e per kWh of grid electricity, 5.3 kg per therm of natural gas, 0.404 kg per mile driven and roughly 0.255 t for a short-haul flight and 1 t for a long-haul flight.

Those averages hide enormous variation. A clean grid, a heat pump, an efficient car and a short commute can cut the total by more than half. Offsetting is best treated as a last step after reducing what you can, and the market for credits varies widely in quality and price. The tree figure is a rough annual sequestration estimate, not a permanent removal.

How the calculation works

Electricity: kWh × 0.386 kg CO₂e.
Natural gas: therms × 5.3 kg CO₂e.
Driving: miles × 0.404 kg CO₂e.
Flights: short-haul ≈ 0.255 t; long-haul ≈ 1.0 t per flight.

Reference values

Illustrative annual footprints
Source	Typical annual use	CO₂e
Electricity	10,000 kWh	3.86 t
Natural gas	500 therms	2.65 t
Car	12,000 miles	4.85 t
Short flights	2	0.51 t
Long flights	1	1.00 t

Worked example: a household footprint

A household using 10,000 kWh of electricity (3.86 t), 500 therms of gas (2.65 t) and 12,000 miles of driving (4.85 t) totals 11.36 tCO₂e before flights. One short-haul return flight adds about 0.51 t; one long-haul return about 2 t. At $15 per tonne, the offset cost is about $170; at $50 per tonne, about $568.

Those averages hide enormous variation. A clean grid, a heat pump, an efficient car and a short commute can cut the total by more than half. Treat offsetting as the last step after reducing what you can, and look for verified, additional and permanent credits rather than the cheapest tonne on the market.

Frequently asked questions

Is offsetting the same as reducing emissions?

No. Reducing avoids emissions in the first place; offsetting pays for reductions elsewhere. A credible climate plan does both, with reduction first.

How much does a tonne of CO₂ offset cost?

Voluntary credits range from a few dollars to over $100 per tonne. Cheap credits often have uncertain additionality; higher-quality removals cost more.

How much CO₂ does a tree absorb?

A mature tree absorbs roughly 20–25 kg per year, but the figure depends on species, climate and age. A newly planted tree takes years to reach that rate.

Is offsetting a substitute for reducing emissions?

No. The standard hierarchy is reduce first, then offset what remains. Offsets vary in quality; look for verified, additional and permanent credits, and be sceptical of very cheap forest credits.

Sources and standards

Emission factors, and the difference between location-based and market-based accounting, follow the Greenhouse Gas Protocol. The page uses published factor sets, states the boundary it assumes, and treats an offset estimate as an order-of-magnitude figure rather than a verified emission reduction.

Greenhouse Gas Protocol — standards and guidance