(Abb: BTU) The quantity of heat required to raise the temperature of one pound of water 1°F at the pressure of 1 atmosphere and temperature of 60°F. See: Calorie. Note: A pound of ice at 32°F requires 144 Btu to melt. One Btu = 257. 996 International Steam Table calories = 778. 26 foot pounds = 1055 joules = about 1/3 watt-hour. One Btu/min = 0. 0236 hp