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Carbon Offset Calculator

Work out the offsets needed to neutralise a given quantity of emissions.

About Carbon Offset Calculator

Offset quality varies widely, so buying a buffer above the nominal requirement is prudent. A mature tree absorbs only about 21 kg of CO2 a year, which is why tree-equivalent figures are so large. Offsets should follow emissions reduction rather than replace it, since permanence and additionality are difficult to verify.

Formula

Carbon Offset

Offsets = emissions ÷ (1 − under-delivery allowance); cost = offsets × price per tonne

under-delivery allowance
Buffer for offsets that deliver less than claimed
21 kg
Approximate annual CO2 absorbed by one mature tree

Worked example

With the default values below, Carbon Offset Calculator returns Offsets Required of 10.625. Change any input above and every figure here is recalculated in your browser.

Inputs used

Annual emissions to offsetminimum 0 t CO2e
8.5 t CO2e
Offset price per tonneminimum 0
25
Allowance for offset under-deliveryaccepts 0–100 %
20 %
Years to offsetaccepts 1–50 years
1 years

Results

Offsets Required
10.625 t CO2e
Annual Offset Cost
$265.63
Total Cost Over the Period
$265.63
Equivalent Trees Planted
506
Effective Cost per Tonne Neutralised
$31.25

Step by step

  1. 1Values used
  2. 2Carbon Offset
  3. 3Offsets Required= 10.625 t CO2e
  4. 4Annual Offset Cost= 265.63
  5. 5Total Cost Over the Period= 265.63
  6. 6Equivalent Trees Planted= 506
  7. 7Effective Cost per Tonne Neutralised= 31.25

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax or fees or charges into account.
  • Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is Carbon Offset calculated?

Offsets = emissions ÷ (1 − under-delivery allowance); cost = offsets × price per tonne Offset quality varies widely, so buying a buffer above the nominal requirement is prudent. A mature tree absorbs only about 21 kg of CO2 a year, which is why tree-equivalent figures are so large.

Why does Carbon Offset matter?

Offsets should follow emissions reduction rather than replace it, since permanence and additionality are difficult to verify.

What values do I need to enter?

This calculator takes 4 inputs: Annual emissions to offset, Offset price per tonne, Allowance for offset under-delivery, Years to offset. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.

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