Convert Cubic Inch to UK Gallon (in³ → gal (UK))

Converting cubic inches to UK gallons is straightforward: multiply by the conversion factor. Follow these three steps to do it by hand or in your head.

1. 1
   Take your value in cubic inches

   Start with the number of cubic inches (in³) you want to convert.
2. 2
   Multiply by 0.003605

   The conversion factor from in³ to gal (UK) is 0.003605. Multiply your value by this number.
3. 3
   Read the result in UK gallons

   The result is your value in UK gallons (gal (UK)).

Multiply the value in cubic inches by 0.003605. For the reverse direction, multiply by 277.41943.

• ✓1 in³ = 16.387 cm³ exactly.
• ✓To convert cubic inches to litres, divide by 61.02.
• ✓US automotive ads today quote both cu in and L for classic cars.

• ✗Confusing in³ with in² or linear inches.
• ✗Using 16 instead of 16.387 on precision machining.
• ✗Assuming modern European engines are marked in cu in — they are always in L or cc.

What is the Cubic Inch?

The cubic inch equals exactly 16.387064 cubic centimeters and is the traditional American unit for engine displacement and small-volume manufacturing measurements. Classic American muscle cars were famously identified by their cubic-inch engine size: the Ford 'Boss 429' had a 429-cubic-inch (7.0-liter) V8, and the Chevrolet 'Big Block 454' was 7.4 liters. Modern American automakers have transitioned mostly to liter-based naming (e.g., 'Hemi 5.7'), but the cubic inch persists in vintage car culture and aviation engines. It is also used for printer-paper coverage and industrial tolerances. The cubic inch relates to the cubic foot (1,728 in³ = 1 ft³), the cubic centimeter (1 in³ ≈ 16.39 cm³), the milliliter (1 in³ ≈ 16.39 mL), and the US fluid ounce (1 fl oz ≈ 1.805 in³).

• Classic US car engine displacement
• Firearms chamber and cartridge specs
• Some US machining and mould design

What is the UK Gallon?

The UK imperial gallon equals exactly 4.54609 liters and is approximately 20% larger than the US gallon. Established by the British Weights and Measures Act of 1824 to standardize earlier ale and corn gallons, the imperial gallon was designed so that 10 pounds of pure water at 62°F occupied exactly 1 gallon. Although the United Kingdom has officially adopted the liter for fuel sales since 1995, the imperial gallon persists in everyday speech ('miles per gallon' for car fuel economy) and remains the standard unit in some Caribbean and Pacific Commonwealth countries. The imperial gallon relates to the US gallon (1 imp gal ≈ 1.201 US gal), the imperial quart (4 imp qt = 1 imp gal), the imperial pint (8 imp pt = 1 imp gal — the famous British pint of beer), and the liter (1 imp gal ≈ 4.546 L).

• UK fuel economy in miles per gallon (UK mpg)
• Older British industrial and brewing contexts
• Commonwealth countries that retain imperial measures