The average bathtub has a capacity of between 75.7 and 170 liters. Whirlpool bathtubs that utilize jets can have a capacity of twice that amount.
Few people fill their bathtubs to capacity when taking a bath, so, on average, a person bathing in a bathtub uses about half that amount. The bat (or bath) is actually a Biblical unit of measurement totalling about 6 gallons or 23 liters. Although showers are often promoted in favor of baths in order to conserve water, more water is consumed during a 10-minute shower than is used during a bath in a bathtub that is half full.