An imperial gallon is exactly 4.54609 liters.
Imperial gallons to Cubic Millimeters Converter — imp gal to mm3
Convert Imperial gallon (imp gal) to Cubic Millimeter (mm3) using the exact conversion factor (1 imperial gallon = 4,546,090 cubic millimeter). See the formula, worked examples, conversion table, history, and common uses.
Imperial gallons to Cubic Millimeters converter
Converter
Volume Converter
Convert metric, US customary, imperial, cooking, dry, and industrial volume units.
Context values
Some unit families need one extra value for a physically accurate result.
Cubic metric volume unit.
Result = input x 0.00454609 / 1e-9.
Volume uses the cubic meter as the base unit.
Reserved above the conversion cards and below the converter.
About Converting Imperial gallons to Cubic Millimeters
Imperial gallon and Cubic Millimeter appear side by side at fuel pumps and on beverage labels, since the US measures liquids in gallons while most of the world uses liters. Imperial gallon is most often used for uk fuel and beverage measurement (historically; uk now primarily uses liters for retail).
Formula
cubic millimeters = imperial gallons × 4546090
This factor comes from each unit's defined relationship to the category's base unit: 1 imperial gallon equals 0.00454609 base units, and 1 cubic millimeter equals 1e-9 base units, so dividing one by the other gives the direct imperial gallon-to-cubic millimeter factor of 4546090.
Simple example
1 imp gal × 4546090 = 4,546,090 mm3
1 imperial gallon = 4,546,090 cubic millimeters.
Real-world example
10 imp gal × 4546090 = 45,460,900 mm3
10 imperial gallons = 45,460,900 cubic millimeters.
Conversion table
| Imperial gallon (imp gal) | Cubic Millimeter (mm3) |
|---|---|
| 1 imp gal | 4,546,090 mm3 |
| 5 imp gal | 22,730,450 mm3 |
| 10 imp gal | 45,460,900 mm3 |
| 25 imp gal | 113,652,250 mm3 |
| 50 imp gal | 227,304,500 mm3 |
| 100 imp gal | 454,609,000 mm3 |
Reverse conversion: Cubic Millimeter to Imperial gallon
1 mm3 × 2.199692e-7 = 2.199692e-7 imp gal
1 cubic millimeter = 2.199692e-7 imperial gallons.
imperial gallons = cubic millimeters × 2.199692e-7
For a page dedicated to this direction, see Cubic Millimeter to Imperial gallon.
Understanding the Imperial gallon
Imperial gallon (imp gal) measures volume. The imperial gallon is defined as exactly 4.54609 liters, about 20% larger than the US gallon. It is classified as a UK/imperial customary unit.
Where it's used: United Kingdom, Canada (some contexts), and other Commonwealth countries
Imperial gallon vs. US gallon. Britain's 1824 Weights and Measures Act defined a new gallon based on 10 pounds of water, replacing the old wine gallon the US had already adopted — leaving the US (3.785 L) and imperial (4.546 L) gallons about 20% apart today.
Uses of the Imperial gallon today
- UK fuel and beverage measurement (historically; UK now primarily uses liters for retail)
- Commonwealth country liquid measurement in some contexts
History of the Imperial gallon
The imperial gallon was created by Britain's Weights and Measures Act of 1824, defined as the volume of 10 pounds of water, replacing several inconsistent older English gallon definitions (wine gallon, ale gallon, corn gallon) with one standard.
Historical origin. Imperial gallon was not the invention of a single named person; it developed through the process described above.
Understanding the Cubic Millimeter (mm3)
Cubic metric volume unit.
Imperial gallon — sources
- UK Weights and Measures Act 1824 — Establishes the imperial gallon definition.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many cubic millimeters are in 1 imperial gallon?
1 imperial gallon equals 4,546,090 cubic millimeters, using the exact defined conversion factor rather than an estimate.
How do I convert imperial gallon to cubic millimeter?
Multiply the imperial gallon value by 4546090. The converter above does this instantly to whatever precision you set.
How do I convert cubic millimeter back to imperial gallon?
Use the reverse factor: 1 cubic millimeter equals 2.199692e-7 imperial gallons. You can also use the swap control in the converter above to flip the direction instantly.
What is a imperial gallon?
Imperial gallon (imp gal) measures volume. The imperial gallon is defined as exactly 4.54609 liters, about 20% larger than the US gallon. It is classified as a UK/imperial customary unit.
What is a cubic millimeter?
Cubic Millimeter (mm3) is a unit of volume.
Is the imperial gallon to cubic millimeter conversion exact?
Yes. The imperial gallon is defined as exactly 4.54609 liters, about 20% larger than the US gallon. That fixed definition is what the converter above uses, so any rounding you see is a display choice, not a limitation of the math.
What is the difference between imperial gallon vs. us gallon?
Britain's 1824 Weights and Measures Act defined a new gallon based on 10 pounds of water, replacing the old wine gallon the US had already adopted — leaving the US (3.785 L) and imperial (4.546 L) gallons about 20% apart today.
Where is the imperial gallon still used today?
United Kingdom, Canada (some contexts), and other Commonwealth countries