Carbon cost calculator: the net present value of your emissions at an internal carbon price
Enter your baseline emissions, an internal carbon price and a planning horizon. The calculator returns the present value of the carbon cost over that horizon, the same figure that appears in Section 4 of a GreenReporting report.
Method last reviewed 14 October 2026. An estimate only, not financial, legal or regulatory advice.
Carbon cost exposure
An estimate only, not financial, legal or regulatory advice.
What this number means
It is today's value of the carbon cost you would carry if you made no reductions and the price applied to every tonne. It is a planning figure for capital allocation and disclosure, not a tax forecast.
Want it in a report?
The wizard carries these inputs through to scenarios, sensitivities and draft disclosures.
How an internal carbon price NPV is worked out
- Start from your baseline emissions in tonnes of CO2e a year.
- Grow them by the annual rate you choose. The default is 2%, applied from year 1.
- Multiply each year's emissions by the carbon price, held constant in today's terms.
- Discount each year's cost to today at your discount rate, 8% by default, with costs falling at year end. The sum is the present value.
An internal carbon price is the amount per tonne a company uses in its own planning. It is not a market price or a legal liability.
| Year | Emissions (tCO2e) | Cost ($) | Discount factor | Present value ($) |
|---|---|---|---|---|
| 1 | 8,160 | 530,400 | 0.9259 | 491,111 |
| 2 | 8,323 | 541,008 | 0.8573 | 463,827 |
| 3 | 8,490 | 551,828 | 0.7938 | 438,059 |
| 4 | 8,659 | 562,865 | 0.7350 | 413,722 |
| 5 | 8,833 | 574,122 | 0.6806 | 390,738 |
| 6 | 9,009 | 585,604 | 0.6302 | 369,030 |
| 7 | 9,189 | 597,317 | 0.5835 | 348,528 |
| 8 | 9,373 | 609,263 | 0.5403 | 329,166 |
| 9 | 9,561 | 621,448 | 0.5002 | 310,879 |
| 10 | 9,752 | 633,877 | 0.4632 | 293,608 |
| Present value of carbon cost | 3,848,668 | |||
Questions about the calculator
What carbon price should I use?
Use the price your company applies in planning. Many companies start from a published scenario or a regulated market price. The calculator holds your chosen price constant and does not forecast one.
Does a rising carbon price change the answer?
Yes, a lot. This calculator holds the price flat in today's terms. The full report also runs a sensitivity with the price rising 4% a year, which raises the result.
Is this the same figure as in the report?
Yes. The worksheet and Section 4 of the report use the same method and the same default assumptions.
Where does the $3,848,668 figure come from?
It is the default example: 8,000 tCO2e, $65 a tonne, 10 years, 2% growth and an 8% discount rate. Change any input to see your own.
Where the carbon cost goes next
IFRS S2 climate reportUK SRS S2 climate reportAASB S2 climate reportEmissions intensity calculator
Enter your numbers and see your own report
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