UK Gallon vs US Gallon
Side-by-side comparison, when-to-use-each guide, and instant conversion. Reviewed for 2026.
UK fuel economy (MPG), some commodity trading, Caribbean nations using UK system.
US fuel pumps (universal), US fuel economy, fuel pricing in Latin America linked to US standards.
| Aspect | UK Gallon | US Gallon |
|---|---|---|
| Volume | 4.546 L | 3.785 L |
| Quarts | 4 | 4 |
| Pints | 8 UK pints (568 ml each) | 8 US pints (473 ml each) |
| Fuel economy comparison | UK MPG figure × 0.83 ≈ US MPG | US MPG × 1.2 ≈ UK MPG |
Frequently asked
My old car says 40 MPG (UK). What's that in US MPG?
40 MPG UK × 0.83 = 33.3 MPG US. The factor is exact: 0.8327. The reason for the difference is purely the bigger UK gallon, not driving habits.
Why do US and UK gallons differ?
After American independence in 1776, the US continued using the older 'wine gallon' (3.785 L) while the UK standardised on a larger 'Imperial gallon' (4.546 L) in 1824. Both are descendants of pre-1776 British units.
Frequently asked questions
My old car says 40 MPG (UK). What's that in US MPG?
40 MPG UK × 0.83 = 33.3 MPG US. The factor is exact: 0.8327. The reason for the difference is purely the bigger UK gallon, not driving habits.
Why do US and UK gallons differ?
After American independence in 1776, the US continued using the older 'wine gallon' (3.785 L) while the UK standardised on a larger 'Imperial gallon' (4.546 L) in 1824. Both are descendants of pre-1776 British units.