One liter of water is equal to 1 kilogram (kg). This is because the density of water is very close to 1 gram per milliliter (g/mL) or 1 kilogram per liter (kg/L) at standard temperature and pressure.
So, if you have 1 kilogram of water, it would occupy a volume of 1 liter. Similarly, if you have 1 liter of water, it would weigh 1 kilogram. This relationship is based on the density of water, which is commonly used as a reference point for converting between mass (kilograms) and volume (liters) in many practical applications.