Greenhouse Gas Equivalents Calculator
Convert any greenhouse gas quantity into CO₂ equivalent tonnes using its Global Warming Potential (GWP). Use it when reporting emissions or comparing the climate impact of different gases.
About this calculator
Different greenhouse gases trap heat at vastly different rates relative to CO₂. To compare them on a common scale, scientists use the concept of Global Warming Potential (GWP), which expresses how much warming a gas causes over a specified time horizon — typically 20 or 100 years — relative to the same mass of CO₂. The conversion formula is: CO₂e = gasAmount × GWP × conversionFactor, where gasAmount is measured in tonnes, GWP is the standardised factor for the chosen gas and time horizon, and conversionFactor accounts for any additional unit or purity adjustments. For example, methane (CH₄) has a GWP of 84 over 20 years or 28 over 100 years (AR6 values), meaning 1 tonne of methane equals 28 tonnes CO₂e over a century. Nitrous oxide (N₂O) has a GWP of 273 over 100 years, and many industrial fluorinated gases have GWPs in the thousands. Selecting the correct time horizon is critical because short-lived gases like methane appear far more potent over 20 years than 100.
How to use
Suppose you want to convert 5 tonnes of methane (CH₄) to CO₂ equivalent using a 100-year GWP of 28 and a conversionFactor of 1. Step 1 — Identify inputs: gasAmount = 5 t, GWP (gasType) = 28, conversionFactor = 1. Step 2 — Apply the formula: CO₂e = 5 × 28 × 1 = 140 tonnes CO₂e. Now suppose the gas is nitrous oxide with GWP = 273: CO₂e = 5 × 273 × 1 = 1,365 tonnes CO₂e. This shows how the same physical mass of different gases can have dramatically different climate impacts, underscoring why choosing the correct gas type matters enormously.
Frequently asked questions
What is Global Warming Potential and why does the time horizon matter?
Global Warming Potential (GWP) is a measure of how much energy a greenhouse gas absorbs over a given period relative to CO₂, which has a GWP of 1 by definition. The time horizon matters because gases break down at different rates in the atmosphere — methane persists for about 12 years, while CO₂ can linger for centuries. Over 20 years methane's GWP is about 84, but over 100 years it falls to 28 because much of it has already decomposed. Choosing a 20-year horizon emphasises near-term warming from short-lived gases, while 100-year GWP is the standard used in most national and corporate emissions reporting.
Which greenhouse gases have the highest CO2 equivalent values?
Fluorinated gases — including sulfur hexafluoride (SF₆), hydrofluorocarbons (HFCs), and perfluorocarbons (PFCs) — have by far the highest GWPs, ranging from hundreds to over 23,000 times the warming impact of CO₂ over 100 years. SF₆, used in electrical switchgear, has a 100-year GWP of approximately 23,500. Although these gases are emitted in much smaller quantities than CO₂ or methane, even tiny leaks can represent enormous CO₂e values. This is why industrial leak detection and gas recovery programs are prioritised in manufacturing and utilities sectors.
How do I use CO2 equivalent values for corporate emissions reporting?
Corporate emissions reporting frameworks such as the GHG Protocol require all greenhouse gas emissions to be reported in CO₂ equivalent tonnes using IPCC-approved GWP values. You calculate CO₂e for each gas separately — using the formula CO₂e = gasAmount × GWP — and then sum all values to arrive at a total Scope 1, 2, or 3 figure. Most frameworks specify using 100-year GWP values from the latest IPCC Assessment Report. Consistent application of GWP factors across reporting periods is essential for tracking progress and enabling meaningful year-over-year comparisons.