How much mass is in a liter

One litre of water has a mass of almost exactly one kilogram when measured at its maximum density, which occurs at about 4 degrees C

One litre of water has a mass of almost exactly one kilogram when measured at its maximal density, which occurs at about 4 °C. Similarly: one millilitre (1 mL) of water has a mass of about 1 g; 1,000 litres of water has a mass of about 1,000 kg (1 tonne).