This online calculator converts volume from UK gallons (Imperial gal) to US liquid gallons (US gal). Factors are based on exact definitions: 1 Imperial gallon = 4.54609 L; 1 US liquid gallon = 3.785411784 L. The ratio is constant and traceable to SI (litre), suitable for engineering, brewing, and logistics.

UK Gallons (Imperial gal) to US Gallons (US gal) Converter

Enter a value in UK gallons (Imperial) to convert it to US liquid gallons.

UK Gallons (Imperial gal)

Result in US Gallons (US gal)

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Calculation process will appear here.
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How to Use

  1. Enter a value in the “UK Gallons (Imperial gal)” field.
  2. Set “Decimal Places” (0–10) to control rounding in the result and the calculation note.
  3. Select “Convert” to compute the equivalent in US gallons.
  4. Use “Copy Result” to copy the numeric output.
  5. Choose “Clear All” to reset inputs, result, and the calculation note.
  6. Press “Swap” button to perform reverse conversion.

Definitions and Unit Facts

UK gallon (Imperial gal, Imp gal) — Imperial unit of volume defined exactly as 4.54609 litres (L). System: Imperial. In US liquid gallons, 1 Imp gal = 4.54609 / 3.785411784 = 1.2009499255 US gal. Widely seen in UK brewing cask sizes and historical fuel measures.

US liquid gallon (US gal) — US customary unit of volume defined exactly as 231 cubic inches, which equals 3.785411784 litres (L). System: US customary. In Imperial terms, 1 US gal = 3.785411784 / 4.54609 = 0.8326741846 Imp gal. Used for beverages, fuels, containers, and retail packaging in the US.

UK Gallons to US Gallons Conversion Calculator

Conversion Formula

US gal = Imp gal × (4.54609 ÷ 3.785411784) = Imp gal × 1.2009499255

Imp gal = US gal × (3.785411784 ÷ 4.54609) = US gal × 0.8326741846

Source: NIST Special Publication 811 — Guide for the Use of the International System of Units (SI), tables listing exact litre relations for US liquid gallon and Imperial gallon

Conversion Table

UK gallons (Imp gal)US gallons (US gal)
0.050.060047
0.10.120095
0.20.240190
0.50.600475
0.80.960760
11.200950
1.21.441140
1.51.801425
22.401900
33.602850
44.803800
56.004750
67.205700
89.607599
1012.009499
1215.011874
1518.014249
2024.018999
2530.023748
3036.028498

Real-World Examples

  • Petrol can labelled 1 Imp gal: 1.2009499255 US gal
  • British “pin” cask 4.5 Imp gal: 5.404274665 US gal
  • British firkin 9 Imp gal: 10.808549330 US gal
  • British kilderkin 18 Imp gal: 21.617098659 US gal
  • British beer barrel 36 Imp gal: 43.234197318 US gal
  • British hogshead 54 Imp gal: 64.851295977 US gal
  • US oil barrel 42 US gal: 34.972315754 Imp gal
  • US half-barrel keg 15.5 US gal: 12.906449862 Imp gal
  • Water cooler 10 US gal: 8.326741846 Imp gal
  • Jerrycan 5 Imp gal: 6.004749628 US gal

What do you use this calculator for? If you want additional volume converters or engineering tools, please tell us in the comments and we will prioritize them.

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