How many UK gallons are in one cubic inch?

One cubic inch equals approximately 0.003604650 Imperial (UK) gallons. The exact factor is derived from 1 UK gallon = 277.4194 in³.

How do I convert cubic inches to UK gallons manually?

Multiply the cubic inch value by 0.003604650. For example, 277.4194 in³ × 0.003604650 ≈ 1.000 UK gal (one full Imperial gallon).

What is the difference between a UK gallon and a US gallon?

One UK (Imperial) gallon = 277.4194 in³ ≈ 4.546 liters. One US liquid gallon = 231 in³ ≈ 3.785 liters. The UK gallon is about 20% larger.

How many cubic inches are in a UK gallon?

One Imperial gallon is defined as exactly 4.54609 liters, which is approximately 277.41943 cubic inches.

Why are there two different gallons?

The Imperial gallon was defined in the British Weights and Measures Act of 1824. The US gallon predates that standardization and remained based on the older Queen Anne wine gallon (231 in³). They diverged and have remained separate units since.

Cubic Inches to UK Gallons Converter

Enter a cubic inch value and get the exact Imperial (UK) gallon equivalent — or convert in reverse.

Cubic Inches to UK Gallons

Cubic Inches (in³)

UK Gallons (Imperial gal)

Common Reference Values

Description	in³	UK gal

Exact factor: 1 in³ = 0.003604650 UK gal
Reverse: 1 UK gal = 277.4194 in³
Note: UK gallon ≈ 20% larger than a US liquid gallon (231 in³).

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Summary

This converter transforms cubic inches (in³) into Imperial (UK) gallons using approximately 0.003604650 UK gal per in³. The Imperial gallon is defined as exactly 4.54609 liters. A bidirectional input lets you reverse the conversion.

How it works

Enter a value in cubic inches in the top input field.
The converter multiplies your value by 0.003604650 (the exact factor for one Imperial gallon).
The result in UK gallons appears instantly.
The formula panel shows the full calculation step by step.
Use the Swap button to reverse direction and convert UK gallons back to cubic inches.

Use cases

Convert fuel tank capacity from cubic inches to Imperial gallons for UK vehicles.
Check engine displacement figures against UK gallon equivalents.
Convert aquarium or barrel volumes for UK brewing and agriculture.
Verify packaging specs that mix US customary and Imperial volume units.
Educational use when learning the difference between US and UK gallon standards.

Frequently Asked Questions

Last updated: 2026-10-05 · Reviewed by Nham Vu