Convert kg Nitrous Oxide (N₂O) to CO₂e
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Nitrous oxide is converted to carbon-dioxide-equivalent by multiplying its mass by its global warming potential (GWP). Under the IPCC’s latest assessment (AR6), one kilogram of N₂O is worth 273 kg CO₂e over 100 years; under the earlier AR5 basis it is 265. Because that multiplier is so large, even small quantities of N₂O — from fertiliser, combustion or manure — carry a heavy CO₂e figure. The converter above reads these values live from the GreenCalculus MasterBrain, shows the source and vintage, and lets you switch the assessment basis.
To convert nitrous oxide (N₂O) to CO₂e, multiply the mass by N₂O’s global warming potential: 273 on the IPCC AR6 100-year basis (265 under AR5). So 1 kg N₂O = 273 kg CO₂e. Divide by the same GWP to reverse it.
kg CO₂e = kg N₂O × GWP. With the AR6 100-year value: kg CO₂e = kg N₂O × 273. Reverse: kg N₂O = kg CO₂e ÷ 273. The multiplier is a global warming potential, not a fixed physical ratio — it depends on the assessment report (AR5 vs AR6) and, in principle, the time horizon, though for N₂O the horizon barely matters (see below).
| Nitrous oxide (N₂O) | × GWP (AR6, 100-yr) | CO₂-equivalent |
|---|---|---|
| 1 kg N₂O | × 273 | 273 kg CO₂e |
| 10 kg N₂O | × 273 | 2,730 kg CO₂e |
| 100 kg N₂O | × 273 | 27,300 kg CO₂e |
| 1,000 kg N₂O (1 t) | × 273 | 273,000 kg CO₂e (273 t) |
The N₂O-to-CO₂e formula (× GWP)
Carbon-dioxide-equivalent restates any greenhouse gas as the mass of CO₂ that would cause the same warming, using the gas’s global warming potential as the exchange rate. For nitrous oxide that rate is 273 — one of the highest among the common inventory gases — because N₂O is both a strong absorber of infrared radiation and very long-lived in the atmosphere.
Why N₂O’s GWP is so high
Two things drive it. Molecule for molecule, N₂O traps far more heat than CO₂; and it persists for over a century before breaking down, so it keeps warming the planet long after it is emitted. The combination gives it a GWP-100 of 273 — meaning a tonne of N₂O does as much 100-year warming as 273 tonnes of CO₂. This is why nitrous oxide, though emitted in small quantities, is a major line in agricultural and combustion inventories.
AR6 (273) vs AR5 (265)
The IPCC revises GWP values with each assessment. The AR6 100-year GWP for N₂O is 273; the older AR5 value, still used by DEFRA and for pre-2021 historical comparison, is 265. State which assessment your inventory uses and hold it constant. The converter’s vintage selector switches between the AR6 and AR5 values the MasterBrain carries.
Nitrous oxide: 273 (AR6) · 265 (AR5). Unlike short-lived methane, N₂O’s GWP is nearly the same on the 20-year and 100-year horizons (both around 273) because it survives in the atmosphere for over a century — so the horizon choice rarely changes the answer.
kg N₂O to kg CO₂e conversion table
The table reads both ways, using the AR6 100-year GWP of 273. The left half converts N₂O mass to CO₂e (× 273); the right half converts a CO₂e figure back to the N₂O mass behind it (÷ 273).
| kg N₂O | → kg CO₂e (× 273) | kg CO₂e | → kg N₂O (÷ 273) |
|---|---|---|---|
| 1 | 273 | 100 | 0.3663 |
| 5 | 1,365 | 500 | 1.832 |
| 10 | 2,730 | 1,000 | 3.663 |
| 50 | 13,650 | 5,000 | 18.32 |
| 100 | 27,300 | 10,000 | 36.63 |
What N₂O’s CO₂e depends on
Because the multiplier is a GWP, the answer depends on the basis — though for N₂O fewer of those choices bite than for methane.
The time horizon barely matters
Methane’s CO₂e swings widely with the time horizon because methane is short-lived. Nitrous oxide is the opposite: with an atmospheric lifetime over 100 years, its 20-year and 100-year GWPs are almost identical (about 273), and it declines only over much longer periods. So while you should still record the horizon, for N₂O it rarely changes the figure — the assessment report (AR6 vs AR5) is the choice that moves the number.
N₂O is not NOx
A frequent confusion: nitrous oxide (N₂O) — “laughing gas” — is a long-lived greenhouse gas with a GWP of 273. The nitrogen oxides (NOx) — nitric oxide (NO) and nitrogen dioxide (NO₂) — are short-lived air pollutants, not directly greenhouse gases, and are reported separately in air-quality inventories, not as CO₂e. This converter is for N₂O only; a NOx figure should never be multiplied by 273.
N₂O ≠ CO₂
Like methane, nitrous oxide produces a genuinely different quantity when converted: a CO₂-equivalent mass 273× the N₂O mass. Its CO₂e is not 1:1 with its mass the way carbon dioxide’s is, which is why a GWP is needed. The same treatment converts methane and the fluorinated gases — see the GWP unit conversion methodology for the general approach.
Where the N₂O-to-CO₂e conversion is used
Nitrous oxide is emitted in small masses from many sources, and its high GWP makes each of them matter.
- Agriculture — the dominant source. Nitrogen fertiliser and managed soils release N₂O; it is usually the largest greenhouse gas on a farm inventory. Estimate it with the fertiliser & soil N₂O calculator (method: the fertiliser & soil N₂O methodology), and manure with the manure management calculator.
- Combustion. Engines and boilers emit small amounts of N₂O alongside CO₂ — captured by the Scope 1 combustion calculator and the mobile combustion methodology.
- The general GWP step. Any inventory line in N₂O is converted to CO₂e by this multiplication; the method is the GWP unit conversion methodology.
Record the basis with the number: assessment report (AR6/AR5) and horizon (100-year). “20 kg N₂O = 5,460 kg CO₂e (AR6, GWP-100)” is auditable; “5,460 kg CO₂e” alone leaves a reviewer unable to tell whether you used 273 or 265. And confirm the figure is N₂O, not NOx.
Frequently Asked Questions
Multiply the mass of nitrous oxide by its global warming potential: kg CO₂e = kg N₂O × GWP. Using the IPCC AR6 100-year value of 273, 1 kg N₂O = 273 kg CO₂e. To reverse it, divide the CO₂e figure by the same GWP.
Over 100 years, the IPCC AR6 GWP of N₂O is 273; the earlier AR5 value is 265. Because N₂O is long-lived, its 20-year GWP is almost the same (about 273). It is one of the highest GWPs among the common inventory gases.
Use 273 if you report on the IPCC AR6 basis (the current standard), or 265 if you follow AR5 (still used by DEFRA and for historical comparison). State which assessment report you use and keep it consistent across the inventory. The converter’s vintage selector switches between them.
N₂O absorbs far more infrared radiation per unit mass than CO₂ and persists in the atmosphere for over a century, so it keeps warming long after it is emitted. The combination gives it a GWP-100 of 273 — a tonne of N₂O does as much 100-year warming as 273 tonnes of CO₂.
No — this is a common and costly confusion. Nitrous oxide (N₂O, “laughing gas”) is a long-lived greenhouse gas with a GWP of 273. The nitrogen oxides (NOx = NO and NO₂) are short-lived air pollutants, not directly greenhouse gases, and are reported in air-quality inventories rather than as CO₂e. Never multiply a NOx figure by 273.
Divide the CO₂e figure by N₂O’s GWP. On the AR6 100-year basis, 1,000 kg CO₂e ÷ 273 = 3.663 kg N₂O. Switch the converter’s direction and it does this for you — make sure you use the same GWP the CO₂e figure was built with.
Barely. Because nitrous oxide lasts over a century, its 20-year and 100-year GWPs are almost identical (about 273), unlike methane whose 20-year value is far higher. The number only falls over much longer horizons. Still record the horizon, but for N₂O the assessment report (AR6 vs AR5) is what moves the figure.
The largest source is agriculture — nitrogen fertiliser and managed soils — followed by manure, combustion in engines and boilers, wastewater, and some industrial processes (nitric and adipic acid). Because of its high GWP, N₂O is often the biggest greenhouse gas on a farm inventory despite the small mass emitted.