text: what is the correct computation for  a circuit breaker? is it 125% or 100% of the total load? where are you using the circuit breaker ? in a house panel the circuit breaker is max sized by the wire and mim sized by the load at 100%. unless the load is a motor then the c/b is oversized 115% or 125%.  the reason is the starting current of the motor and if it has a 60 or 90 c rating. please read the (nationa electrical code 2005) for more information.