Volume Converter

The liter is the SI unit of volume used in everyday measurement. This converter covers six units: liters, milliliters, US gallons, US fluid ounces, US cups, and cubic feet. 1 US gallon = 3.785411784 liters (exact, NIST SP 811). Type any value and all others update instantly; click any result to make it the input.

The formula

All conversions route through the liter as base:

target = value × (fromUnit_to_L / toUnit_to_L)

For US gallons to liters:

L = gal × 3.785411784

For liters to US fluid ounces:

fl oz = L × (1 / 0.0295735295625) = L × 33.814

Practical examples

Example 1 — Fuel for a US road trip (gallons to liters)

A car has a 15-gallon fuel tank. A European traveler wants to know the capacity in liters.

15 × 3.785411784 = 56.78 L

Example 2 — Water bottle comparison (fluid ounces to milliliters)

A 32 fl oz water bottle — how many milliliters is that?

32 × 29.5735295625 = 946.35 mL (almost exactly 1 liter)

Example 3 — Fish tank size (cubic feet to liters)

A fish tank measures 2 cubic feet. What is the capacity in liters?

2 × 28.316846592 = 56.63 L

Common mistakes

Mistake 1 — Confusing US gallon and UK imperial gallon

The US gallon is 3.785 L; the UK imperial gallon is 4.546 L — about 20% larger. A British recipe that calls for "1 gallon" may mean the larger imperial gallon. This converter uses the US gallon exclusively.

Mistake 2 — Confusing US fluid ounce and UK fluid ounce

The US fluid ounce is 29.574 mL; the UK fluid ounce is 28.413 mL. The difference is about 4%. In large quantities — say, 32 oz — this is a 37 mL discrepancy.

International and regional variations

Quick reference: common volume conversions