Convert US Gallon to Imperial Gallon
Convert us gallons to imperial gallons instantly. 1 us gallon = 0.8326741846 imperial gallon — use the live calculator, the exact formula, a conversion table and worked examples. Also check the Imperial Gallon to US Gallon converter for the reverse conversion.
Units explained
US Gallon
The US liquid gallon is defined as exactly 231 cubic inches (3.785411784 liters).
Based on the English wine gallon of 231 cubic inches, retained by the US after 1824.
The primary US unit for fuel, milk and large beverage containers.
English wine gallon; US since 1824.
Imperial Gallon
The imperial gallon is defined as exactly 4.54609 liters.
Set by the British Weights and Measures Act of 1824 as the volume of 10 lb of water.
Used for fuel and beverages in the UK and Commonwealth.
UK, 1824.
US Gallon to Imperial Gallon conversion formula
The relationship between us gallons and imperial gallons:
To convert us gallons to imperial gallons, multiply the value in us gallons by 0.8326741846. To reverse, multiply imperial gallons by 1.2009499255.
How to use this converter
Type a value into the calculator. The result in imperial gallons updates as you type. Tap a quick value, copy the result with one click, or use the swap arrow to jump straight to the Imperial Gallon to US Gallon converter for the reverse direction.
Step-by-step: convert us gallons to imperial gallons
- Write down the value in us gallons (gal).
- Multiply that value by the factor 0.8326741846.
- The product is the equivalent value in imperial gallons (gal).
- To reverse, multiply the imperial gallon value by 1.2009499255.
Worked examples
Example 1 — Convert 1 gal to gal:
1 × 0.8326741846 = 0.8326741846 gal
Example 2 — Convert 100 gal to gal:
100 × 0.8326741846 = 83.2674184629 gal
Real-world example — Hardware-scale dimensions
A 10-us gallon fastener or component is about as long as a thumbnail. Mechanics and DIY enthusiasts convert between us gallons and imperial gallons daily when mixing metric and imperial tools.
10 gal × 0.8326741846 = 8.3267418463 gal
Real-world example — Postcard and small-object dimensions
A postcard is about 5 us gallons wide. Converting to imperial gallons is essential for international postal addressing forms that ask for dimensions in different units across countries.
5 gal × 0.8326741846 = 4.1633709231 gal
Real-world example — Ruler-scale measurements
A 30-us gallon school ruler converts cleanly to imperial gallons — useful when buying a desk accessory from a retailer whose product specs use a different unit.
30 gal × 0.8326741846 = 24.9802255389 gal
US Gallon to Imperial Gallon conversion table
Standard reference values for converting us gallons to imperial gallons:
| US Gallon [gal] | Imperial Gallon [gal] |
|---|---|
| 0.01 | 0.0083267418 |
| 0.1 | 0.0832674185 |
| 1 | 0.8326741846 |
| 2 | 1.6653483693 |
| 3 | 2.4980225539 |
| 4 | 3.3306967385 |
| 5 | 4.1633709231 |
| 10 | 8.3267418463 |
| 20 | 16.6534836926 |
| 30 | 24.9802255389 |
| 40 | 33.3069673852 |
| 50 | 41.6337092314 |
| 100 | 83.2674184629 |
| 500 | 416.3370923145 |
| 1000 | 832.674184629 |
Frequently asked questions
How many imperial gallons is 1 us gallon?
How do I convert us gallons to imperial gallons?
How do I convert imperial gallons back to us gallons?
How many imperial gallons is 100 us gallons?
Popular volume unit conversions
Convert US Gallon to other volume units
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Metric / SI (15 units)
US Customary (Liquid) (14 units)
US Customary (Dry) (5 units)
Imperial (UK) (14 units)
Cubic (length-derived) (4 units)
Cooking / Culinary (5 units)
Sources & references
Conversion factor (1 gal = 0.8326741846 gal) verified against the following authoritative sources:
- BIPM — The International System of Units (SI Brochure 9th ed.)
Official BIPM publication defining the seven SI base units (including the meter) and the rules for their use. The global authority on units of measurement.
- NIST — Guide to the SI
US National Institute of Standards and Technology reference covering the SI base and derived units with definitions and usage rules for US technical practice.
- NIST Special Publication 811 — Guide for the Use of the International System of Units
Detailed NIST guide covering exact conversion factors between SI and US customary units along with formatting and rounding conventions.
- NIST — Refinement of values for the yard and pound (Federal Register 1959)
The treaty (signed by US
- International Astronomical Union — System of Astronomical Constants
The IAU defines astronomical units including the AU (149597870700 m exactly) light-year and parsec used in astronomy and astrophysics.