Table of Contents
Educational volume and energy conversions with explicit unit conventions. Fuel energy and emissions examples are approximate accounting models, not universal fuel properties. Equations use a decimal point.
1US and Imperial volume units
The petroleum barrel uses US liquid gallons. An Imperial gallon is a different volume; it cannot replace the US gallon in the barrel equation. The litre figures for the barrel and US gallon below are rounded, while the Imperial gallon definition is exact. [1] 1 bbl = 42 US gal ≈ 158.9873 L. 1 US gal ≈ 3.785412 L; 1 Imperial gal = 4.54609 L.
2Btu, therm and calorie conventions
Btu has several definitions. Here Btu_IT means the International Table convention. The US and EC therm conversions are listed separately rather than treating 100000 Btu_IT as an exact US therm. cal_th denotes the thermochemical calorie. [1] 1 Btu_IT ≈ 1055.056 J; 1 cal_th = 4.184 J. 1 therm (US) = 105480400 J; 1 therm (EC) = 105506000 J. 1 kWh = 3600000 J.
3A sourced energy and CO₂ example
The EPA oil-equivalency example uses 5.80 MMBtu per barrel and 20.31 kg of carbon per MMBtu, assuming all carbon is oxidized. With MMBtu = one million Btu, its rounded result is 0.43 metric tonnes of CO₂ per barrel. This is a combustion estimate, excluding upstream and other lifecycle emissions. Heat content and carbon composition vary between fuels; these assumptions are not universal constants. The GJ figure below uses Btu_IT as the stated energy convention. [1][2] 5.80 × 10^6 Btu_IT ≈ 6.12 GJ. 5.80 × 20.31 × (44 / 12) / 1000 ≈ 0.43 t CO₂/bbl.
Results depend on the stated assumptions. Sources checked on 2026-10-03.
