What is Imperial gallon?
An Imperial gallon is a volume unit used in the United Kingdom equal to approximately 4.546 litres. It is larger than the US gallon and is commonly referenced for fuel efficiency (miles per gallon) in the UK.
Real-world uses
Imperial gallons are used in the United Kingdom, Canada (for some purposes), and several Caribbean countries. British fuel economy was historically quoted in miles per Imperial gallon. Older Commonwealth-era recipes and industrial specifications may reference Imperial gallons.
History
The Imperial gallon was established by the British Weights and Measures Act of 1824 as the volume occupied by 10 pounds of water at 62°F (≈ 17°C). It replaced several older gallon definitions including the wine gallon (retained by the US) and the ale gallon.
Common mistakes
Assuming the Imperial gallon equals the US gallon. The Imperial gallon is about 4.546 litres versus 3.785 litres for the US gallon. Converting mpg figures between the two systems without adjusting for gallon size gives misleading results.
What is cubic metre?
A cubic metre is the SI unit of volume, equal to a cube with one-metre sides. It is used in construction, water supply, industrial gas storage, and large-scale fluid measurement.
Real-world uses
Cubic metres are used for water and natural gas billing, concrete volumes in construction, shipping container capacities, and lumber measurement. Swimming pools, reservoirs, and water tanks are specified in m³. One m³ of water weighs one metric tonne.
History
The cubic metre is an SI-derived unit following naturally from the metre. It became the standard volume unit for large quantities in engineering and commerce. Water utilities worldwide adopted it as their billing unit, replacing older local measurements.
Common mistakes
Forgetting that 1 m³ = 1,000 litres, not 100. Also, confusing cubic metres with square metres—m³ is volume while m² is area. A small error in linear dimensions leads to large volumetric errors because volume scales cubically.
When is this conversion used?
Converting between Imperial gallon and cubic metre is common when working across metric and imperial systems, such as international trade, travel between countries with different measurement standards, or following instructions from a different region.
Worked examples
1 Imperial gallon = 0.00454609 cubic metre
1 cubic metre = 1,000 litre
How to convert Imperial gallon to cubic metre
To convert Imperial gallon to cubic metre, multiply the value by 0.00454609.
To convert cubic metre back to Imperial gallon, multiply by 219.9692483.
Measurement standards
The cubic metre is the SI derived unit of volume. The litre, equal to exactly one cubic decimetre (0.001 m³), is accepted by the BIPM for use alongside SI units. Both the lowercase "l" and uppercase "L" are approved symbols for the litre.
Did you know?
An Olympic swimming pool holds 2,500 cubic metres of water — about 2.5 million litres. The Amazon River discharges roughly 209,000 cubic metres per second, enough to fill 84 Olympic pools every single second.
Quick reference: Imperial gallon to cubic metre
| Imperial gallon | cubic metre |
|---|---|
| 0.1 | 0.00045461 |
| 0.5 | 0.00227305 |
| 1 | 0.00454609 |
| 2 | 0.00909218 |
| 5 | 0.02273045 |
| 10 | 0.0454609 |
| 25 | 0.11365225 |
| 50 | 0.2273045 |
| 100 | 0.454609 |
| 250 | 1.1365225 |
| 500 | 2.273045 |
| 1,000 | 4.54609 |
Common values
| Imperial gallon | cubic metre | |
|---|---|---|
| A teaspoon | 0.00109985 Imperial gallon | 0.000005 cubic metre |
| A cup of coffee | 0.05499231 Imperial gallon | 0.00025 cubic metre |
| A water bottle | 0.10998462 Imperial gallon | 0.0005 cubic metre |
| A bathtub | 65.99077449 Imperial gallon | 0.3 cubic metre |
| A swimming pool (Olympic) | 549,923.12074772 Imperial gallon | 2,500 cubic metre |
Available Volume units
More Imperial gallon conversions
- Convert Imperial gallon to litre
- Convert Imperial gallon to millilitre
- Convert Imperial gallon to US gallon
- Convert Imperial gallon to cubic metre
- Convert Imperial gallon to US fluid ounce
- Convert Imperial gallon to Imperial fluid ounce
- Convert Imperial gallon to teaspoon (metric)
- Convert Imperial gallon to tablespoon (metric)
- Convert Imperial gallon to cubic centimetre