CO₂-Equivalent (GWP) Greenhouse Gas Calculator

Enter Calculation

CO₂ mass (kg)

CH₄ (methane) mass (kg)

N₂O (nitrous oxide) mass (kg)

HFC mass (kg)

GWP for CH₄ (100-yr, default 28)

GWP for N₂O (100-yr, default 265)

GWP for HFC (e.g. HFC-134a = 1430)

Results

Total CO₂-Equivalent Emissions

1,810

kg CO₂e (= 1.81 tonnes CO₂e)

Gas	CO₂e contribution (kg)
CO₂	1,000
CH₄ (methane)	280
N₂O (nitrous oxide)	530
HFC	0

What is CO₂-equivalent (CO₂e)?

Different greenhouse gases trap heat with very different intensities. To compare them on a single scale, scientists use the Global Warming Potential (GWP) — the warming caused by one tonne of a gas relative to one tonne of carbon dioxide over a chosen time horizon (usually 100 years). Multiplying the mass of each gas by its GWP and adding the results gives the total CO₂-equivalent (CO₂e) — a universal currency for carbon accounting and footprint reporting.

Each greenhouse gas is multiplied by its GWP factor to express warming impact as a single CO₂e figure.

How to use this calculator

Enter the mass (in kilograms) of each gas you emitted. CO₂ has a GWP of 1 by definition. The default GWP factors follow the IPCC AR5 100-year values: methane (CH₄) ≈ 28 and nitrous oxide (N₂O) ≈ 265. HFCs vary widely, so adjust the HFC GWP to match your refrigerant (e.g. HFC-134a ≈ 1430). The calculator returns total CO₂e in kilograms and tonnes, plus the contribution of each gas.

The formula explained

The core equation is simply $$\text{CO}_2\text{e} = \text{CO}_2 + \text{CH}_4 \cdot \text{GWP}_{\text{CH}_4} + \text{N}_2\text{O} \cdot \text{GWP}_{\text{N}_2\text{O}} + \text{HFC} \cdot \text{GWP}_{\text{HFC}}$$ Because GWP is dimensionless and relative to CO₂, a small mass of a high-GWP gas can dominate the total. For example, 1 kg of methane (GWP 28) contributes as much warming as 28 kg of CO₂.

Relative 100-year Global Warming Potential of common gases (CO₂ = 1).

Worked example

Suppose you emit 1,000 kg CO₂, 10 kg CH₄ and 2 kg N₂O. Using GWP factors of 28 and 265: \(\text{CO}_2 = 1{,}000\); \(\text{CH}_4 = 10 \times 28 = 280\); \(\text{N}_2\text{O} = 2 \times 265 = 530\). Total = $$1{,}000 + 280 + 530 = 1{,}810 \text{ kg CO}_2\text{e}$$ 1,810 kg CO₂e, or 1.81 tonnes CO₂e.

FAQ

Which GWP values should I use? Most modern inventories use IPCC AR5 100-year values (CH₄ = 28, N₂O = 265). Older reports may use AR4 (CH₄ = 25, N₂O = 298). You can override the factors in the form.

Why is methane sometimes given as 84? That is the 20-year GWP, which weights short-term warming more heavily. The 100-year value (28) is the standard for national reporting.

Do I include CO₂ from biomass? Biogenic CO₂ is often reported separately; include only the sources required by your reporting standard.