What is a Liter?

The liter equals exactly 1 cubic decimeter (1 dm³ = 0.001 m³) and is the everyday metric unit for liquids worldwide. Adopted as part of the metric system in the 1790s, the liter is used universally for beverages, fuel, household chemicals, and cooking liquids — except in the United States where gallons and fluid ounces dominate. The liter has special connection to mass: pure water at 4°C has almost exactly 1 kg per liter, a relationship designed into the metric system. Soda, milk, and water bottles in metric countries come in 0.5 L, 1 L, 1.5 L, and 2 L sizes. The liter relates to the milliliter (1,000 mL = 1 L), the cubic meter (1,000 L = 1 m³), the US gallon (1 L ≈ 0.264 gal), and the UK gallon (1 L ≈ 0.220 imp gal). Although not strictly an SI base unit, the liter is one of the most-used metric units globally.

Visual reference for how the liter relates to other volume units. Each row links to the full converter for that pair.

See all 15 volume units in matrix view →

• Bottled beverages and milk in Europe
• Petrol and diesel pricing in metric countries
• Engine displacement (car engines rated in litres)

• ✓1 L = 1000 ml = 1 dm³ = 0.001 m³ exactly.
• ✓1 L of water weighs 1 kg at 4 °C — use for quick mass estimates.
• ✓Fuel economy in Europe is litres per 100 km; lower is better. US uses mpg where higher is better.

• ✗Confusing L (litre) with l (lowercase), since lowercase l can be mistaken for digit 1. Capital L is preferred.
• ✗Mixing litres and US gallons in fuel economy discussions.
• ✗Writing engine displacement in ml instead of L — 1500 cc = 1.5 L.