The formula
L = UK gal × 4.54609
Where the factor comes from — each unit by its definition, then its size in SI:
1 UK gal = 4.54609 × L = 0.00454609 m³1 L = m³ / 1000 = 0.001 m³
Dividing the two SI sizes gives the factor: 4.54609, exact — every step above is a definition, not a measurement. The reverse factor is 0.219969248299.
The cubic metre is the SI unit of volume; the litre is exactly one thousandth of it. The US and UK gallons are different sizes, which is why a fuel-economy figure in mpg depends on which country printed it.
Worked examples
- A soft-drink bottle: 0.439938 UK gal = 2 L — 0.439938 × 4.54609 = 2
- A paint bucket (5 US gal): 4.16337 UK gal = 18.9271 L — 4.16337 × 4.54609 = 18.9271
- A water tank (1 m³): 219.969 UK gal = 1,000 L — 219.969 × 4.54609 = 1,000
- A drinks can (330 mL): 0.0725899 UK gal = 0.33 L — 0.0725899 × 4.54609 = 0.33
Frequently asked questions
How many litres is 1 UK gal?
1 UK gal = 4.54609 L, exactly, from the unit definitions.
How do I convert litres back to UK (imperial) gallons?
Divide by 4.54609 — or multiply by 0.219969248299: 1 L = 0.219969248299 UK gal.