A United States (US) buyer's sustainability form asks for fuel in gallons or barrels. How do I convert my litres or tonnes?

Use the Petroleum Planning and Analysis Cell (PPAC) Ready Reckoner: 1 US gallon is 3.78 litres, 1 US barrel is 159 litres or 42 gallons, and 1 kilolitre is 6.29 barrels. So 1,000 litres is 264.6 gallons or 6.29 barrels. Check the form means US gallons.

The PPAC conversions

• Table 9.3, Volume conversion: 1 US barrel = 159 litres. 1 US gallon = 3.78 litres. 1 kilolitre = 6.29 barrels. 1 US barrel = 42 gallons.
• Table 9.2 gives barrels per tonne: petrol 8.88, diesel 7.61, kerosene 8.08, aviation turbine fuel 8.10, light diesel oil 7.37, furnace oil 6.74. PPAC does not label them with a temperature. I read them as the 29.5 degree Celsius basis because 1.411 x 6.29 = 8.875 for petrol.
• Table 9.5 gives energy: 1 million British thermal units (MMBtu) = 252,000 kilocalories. At PPAC's 4.19 kilojoules per kilocalorie that is 1,055.9 megajoules.

Rounding you will see

• 159 / 42 = 3.786 litres per gallon, so PPAC's 3.78 is a rounded figure. Working from 3.78 gives 264.55 gallons per 1,000 litres. Working from 159 litres and 42 gallons gives 264.15. The gap is 0.15%.
• Both are small next to normal receipt rounding. Pick one route and use it for every line on the form.
• PPAC lists only the US gallon. If a form says gallons and the buyer is not in the US, ask which gallon it means.

From litres, tonnes or energy

1. Litres to US gallons: divide by 3.78. Litres to barrels: divide by 159.
2. Tonnes to gallons: take PPAC's litres per tonne and divide by 3.78. Diesel: 1,210 / 3.78 = 320.1 gallons a tonne. Petrol: 1,411 / 3.78 = 373.3. Furnace oil: 1,042.4 / 3.78 = 275.8.
3. Those use the 29.5 degree basis. A bulk invoice at 15 degrees needs the PPAC multiplier first. The fuel-volume answer on this site lists them.
4. If the form asks for million British thermal units of gas, convert from your bill's printed energy. The piped natural gas (PNG) bill answer shows how.

8,000 litres of diesel on a US buyer's table

• US gallons: 8,000 / 3.78 = 2,116.4
• Barrels: 8,000 / 159 = 50.3
• Check through barrels: 50.31 x 42 = 2,113.2 gallons, 0.15% lower
• Tonnes route: 8,000 / 1,210 = 6.61 tonnes at the 29.5 degree basis. Write litres, gallons and basis on the form

The litres are an example. Say which route you used in the form's notes.

What Senseible does here

Senseible reads fuel invoices and electricity bills into monthly records, in the litres or kilograms the invoice prints. Convert to gallons or barrels only for the buyer's form and keep the invoice figure as the record.

• US buyer asks for EPA factors
• Litres in a tonne of diesel in India
• Fuel volume at 29.5 C or 15 C
• PNG bill in SCM or MMBtu to CO2

Sources: PPAC Ready Reckoner 2025-26, Tables 9.2, 9.3 and 9.5

Last reviewed 2026-11-05. Check the buyer's form for the unit it defines. Some forms specify a temperature or an energy basis.