Gallon to Milliliters Calculator

This converter turns gallons into milliliters (and vice versa) using exact, widely accepted conversion factors. It supports US liquid gallons and metric subunits such as milliliters, centiliters and liters. Use the entry box above to type a value, pick the units and press Convert.

Exact conversion

• US (liquid) gallon → milliliters: 1 US gal = 3,785.411784 mL.
• Imperial (UK) gallon → milliliters: 1 UK gal = 4,546.09 mL.
• Milliliter definition: 1 mL = 1 cubic centimeter (1 cm³) = 1/1,000 of a liter.

Conversion formula

• To convert gallons to milliliters:
• milliliters = gallons × 3,785.411784 (for US liquid gallons)
• Example: 2.5 gal × 3,785.411784 = 9,463.52946 mL.

Useful quick reference table

• 1 gal = 3,785.411784 mL
• 0.5 gal = 1,892.705892 mL
• 0.25 gal = 946.352946 mL
• 0.1 gal = 378.5411784 mL
• 5 gal = 18,927.05892 mL
• 10 gal = 37,854.11784 mL.

When to use the US vs Imperial gallon

If your recipe, label or specification is American (gallons on US packaging, fuel economy in the U.S.), use the US liquid gallon factor (3,785.411784 mL). If the context is British or certain Commonwealth references, check whether the imperial gallon (4,546.09 mL) is intended. If in doubt, choose liters or milliliters to avoid ambiguity.

Practical tips

• For cooking and everyday tasks, rounding the final mL to the nearest whole number is usually fine (for example, 3,785 mL).
• For laboratory or engineering calculations, keep at least six significant figures or follow the tolerance specified in the original data. The exact multipliers above are provided when you need full precision.
• Common mistake: confusing US dry gallon (rare) or imperial gallon with the US liquid gallon these are not interchangeable. When reading labels, prefer metric values when available.

FAQs

Q1. Is the gallon always the same?

A: No. “Gallon” refers to different sizes depending on the system: US liquid gallon (3,785.411784 mL) and the UK/imperial gallon (4,546.09 mL). Always confirm which system your source uses.

Q2. Why do results sometimes look long (many decimals)?

A: The calculator uses exact factors to avoid rounding errors. You can round the displayed result to the number of decimal places you need for readability.

Q3. Can I convert small and very large amounts?

A: Yes, this tool handles tiny volumes (fractions of a gallon) and very large ones (dozens or thousands of gallons) with the same accuracy.