Select the unit you wish the table to convert from Select type of Btu Btu (15°C) Btu (15.6°C) Btu (15.8°C, Canada) Btu (15.8°C, ISO) Btu (3.9°C) Btu (I.T.) Btu (I.T., pre-1956) Btu (mean) Btu (thermoc.)