Electric Formulas

As a service to you, below are some of the more common electrical formulas. Feel free to print this page out for your convenience.

TO FIND SINGLE-PHASE THREE-PHASE DIRECT CURRENT Kilowatts I x E x PF 1000 I x E x 1.732 x PF 1000   I x E   1000 KVA I x E 1000 I x E x 1.732 1000 --------------- Horsepower (Output) I x E x %EFF x PF 746 I x E x 1.732 x %EFF x PF 746 I x E x %EFF 746 Amperes when Horsepower is known       HP x 746       E x %EFF x PF            HP x 746            1.732 x E x %EFF x PF   HP x 746   E x %EFF Amperes when Kilowatts is known   KW x 1000   E x PF     KW x 1000     1.732 x E x PF   KW x 1000   E Amperes when KVA is known KVA x 1000 E KVA x 1000 1.732 x E ---------------

E = Volts I = Amperes %EFF = Percent Efficiency PF = Power Factor

Useful Formulas

BTUs x 777.5 = foot pounds BTUs x 3.93 ÷ 10,000 = horsepower hours BTUs x 2.93 ÷ 10,000 = Kilowatt hours BTUs per minute x 13.0 = foot pounds per second BTUs per minute x 1.76 ÷ 100 = Kilowatts BTUs per hour x 2.93 ÷ 10,000 = Kilowatts BTUs per hour x 2.98 ÷ 1,000,000 = Boiler horsepower (Celsius x 9 ÷ 5) + 32 = Fahrenheit Circular mils x 0.7854 = Square mils (Fahrenheit - 32) x 5 ÷ 9 = Celsius Foot pounds x 2.29 ÷ 1,000 = BTUs Foot pounds x 5.05 ÷ 10,000,000 = Horsepower hours Foot pounds x 3.77 ÷ 10,000,000 = Kilowatt hours Foot pounds per minute x 1.29 ÷ 1,000 = BTUs per minute Foot pounds per minute x 3.03 ÷ 100,000 = Horsepower Foot pounds per second x 1.82 ÷ 1,000 = Horsepower Horsepower x 42.4 = BTUs per minute Horsepower x 33,000 = Foot pounds per minute Horsepower x 550 = Foot pounds per second Horsepower x 0.746 = Kilowatts Horsepower boiler x 33520 = BTUs per hour Horsepower boiler x 9.80 = Kilowatts Horsepower hours x 2550 = BTUs Horsepower hours x 1,980,000 = Foot pounds Kilowatts x 56.9 = BTUs per minute Kilowatts x 3412 = BTUs per hour Kilowatts x 1.341 = Horsepower Kilowatt hours x 3412 = BTUs Kilowatt hours x 1.34 = Horsepower hours Square inch x 273,000 = Circular mils