Gallon-atmosphere (UK) to horsepower-hour conversion calculator shown above calculates how many horsepower-hour are in 'X' gallon-atmosphere (UK) (where 'X' is the number of gallon-atmosphere (UK) to convert to horsepower-hour). In order to convert a value from gallon-atmosphere (UK) to horsepower-hour (from gal atm to hph) type the number of gal atm to be converted to hph and then click on the 'convert' button.