Because psi measures pressure and ft-lbs measures total energy, pounds per square inch cannot be translated to ft-lbs. Neither one is used as the main unit of measurement in the International System of Units. Psi and ft-lbs are mainly British and American units of measurement.
The International System of Units allows for the conversion of psi and ft-lbs into the corresponding units. 6,895 Pascals, or 6,895 Newtons per metre, are equivalent to one psi. Energy in the form of one ft-lb is equal to 1.356 joules. James Watt, an engineer, created it to explain how much labour a horse can accomplish in a certain amount of time.