Question: 1 litre of water weighs how many kg?
Answer: One litre of water has a mass of almost exactly one kilogram when measured at its maximal density, which occurs at about 4 °C. It follows, therefore, that 1000th of a litre, known as one millilitre (1 mL) of water has a mass of about 1 g; 1000 litres of water has a mass of about 1000 kg (1 tonne).