Understand the relationship
Visual explanation
The US system and the British Imperial system developed with different gallon definitions. That difference continues through their pints and fluid ounces.
Both gallons contain eight pints, but the pints are system-specific. A US pint is 473.176473 mL; an Imperial pint is 568.26125 mL. Fluid-ounce counts also differ: 128 per US gallon and 160 per Imperial gallon.
Calculate it
The formula
1 Imperial gal ≈ 1.200949926 US galInstant converter
Convert while you learn
1 US gallon equals
Imperial gallons
Calculated from the canonical unit dataset.
1 × 3785.411784 mL ÷ 4546.09 mL
Follow the reasoning
Worked examples
Compare 1 gallon in liters.
4.54609 − 3.785411784 = 0.760678216The Imperial gallon holds 0.760678216 L more.
Convert 5 Imperial gallons to liters.
5 × 4.54609 = 22.730455 Imp gal = 22.73045 L
Convert 5 US gallons to liters.
5 × 3.785411784 = 18.927058925 US gal = 18.92705892 L
Quick lookup
US gallon to Imperial gallons chart
| US gallons | Imperial gallons |
|---|---|
| 1 | 0.83267418463 |
| 2 | 1.6653483693 |
| 5 | 4.1633709231 |
| 10 | 8.3267418463 |
Values are generated from the same canonical constants used by the converter. Decimal display may be rounded.
Common mistake
Check the unit and direction
Never infer the system from the word “gallon” alone. Look for US, Imperial, a country context, or the stated liter value.
Remember it
Attach the system label every time: write “US gal” or “Imp gal,” never just “gal” in an international calculation.
Quick practice
Which is larger: 3 US gallons or 3 Imperial gallons?
3 Imperial gallons. They equal 13.63827 L, while 3 US gallons equal 11.356235352 L.
Accuracy note: Core U.S. liquid relationships and the 231-cubic-inch gallon were checked against NIST Handbook 44 (2026), Appendix C. SI definitions were checked against NIST SI Units—Volume. Imperial values were checked against the UK Weights and Measures Act 1985. Values were last checked on . Review the source list.