General
Gallon Calculator
Convert between US gallons, UK (Imperial) gallons, and other volume units
Reviewed by the calculator.uk.com Team · Last reviewed 26 May 2026 · Our methodology
Enter a value and select units to see the conversion result
Related to Gallon Calculator
The Gallon Calculator is a comprehensive volume conversion tool that allows you to convert between US gallons, UK (Imperial) gallons, and various other volume units. The calculator uses precise conversion factors based on international standards to ensure accurate results for all conversions.
Key Conversion Factors
• 1 US Gallon = 3.78541 Liters
• 1 UK (Imperial) Gallon = 4.54609 Liters
• 1 US Gallon = 0.83267 UK Gallons
• 1 US Gallon = 128 Fluid Ounces
• 1 US Gallon = 16 Cups
• 1 US Gallon = 8 Pints
• 1 US Gallon = 4 Quarts
The calculator first converts the input value to US gallons as an intermediate step, then converts it to the desired output unit. This two-step process ensures consistency and accuracy across all conversions, as all conversion factors are standardized relative to US gallons.
The calculator displays results with appropriate precision based on the magnitude of the numbers involved. For values less than 100, three decimal places are shown to maintain accuracy for small quantities. For larger values, two decimal places are used as this is typically sufficient for practical purposes.
US vs UK Gallons
It's important to note that US and UK gallons are different units. A UK (Imperial) gallon is approximately 20% larger than a US gallon. When working with recipes, fuel efficiency, or other measurements, always check which gallon unit is being referenced to avoid conversion errors.
The calculator handles all common volume units used in cooking, industry, and general measurements. For very precise scientific work, consider using metric units (liters, milliliters, or cubic meters) as these are the international standard units for volume measurement.
1. Why are there different types of gallons?
US and UK gallons evolved separately from different historical measurement systems. The US gallon is based on the wine gallon (231 cubic inches), while the UK gallon was standardized as the volume of 10 pounds of water at a specific temperature. This historical difference explains why they have different volumes today.
2. Which gallon should I use?
Use US gallons for measurements in the United States and most of North America. Use UK (Imperial) gallons for measurements in the United Kingdom and some Commonwealth countries. For international or scientific work, it's best to use metric units (liters) to avoid confusion.
3. How accurate are these conversions?
The conversions are highly accurate, using precise conversion factors established by international standards organizations. The calculator maintains 3 decimal places for small values and 2 decimal places for larger values, which is more than sufficient for most practical applications.
4. Can I use this calculator for any type of liquid?
Yes, these volume conversions are valid for any liquid since they only deal with volume (the space occupied) rather than mass or density. However, when working with specific substances where mass is important, you should also consider the density of the liquid.
5. What is the scientific source for this calculator?
US and Imperial gallons are two historical definitions that never fully reconciled: the US gallon derives from the old English wine gallon (231 cubic inches, or exactly 3.785411784 liters), while the Imperial gallon was redefined in 1824 as the volume of 10 pounds of water and equals exactly 4.54609 liters. Both figures are maintained today as fixed definitions by NIST and UK measurement authorities, so converting between them, or into quarts, pints, and fluid ounces, is exact arithmetic rather than estimation. This is also why a gallon means a meaningfully different volume depending on which country's convention is in use.