Electrical calculators

Size a conductor in AWG or mm², check the volt drop on a long run, solve for volts, amps, resistance or watts, and read a resistor’s bands. Every tool runs in your browser and shows the formula it used.

Calculators

• Wire sizeThe gauge a run needs to stay inside its voltage drop allowance, in AWG or mm².
• Voltage dropVolts lost, percentage and voltage left at the load for a cable you already have.
• Ohm's lawAny two of V, I, R and P in; the other two out, with the stock values that come closest.
• Amps, watts and voltsNameplate to current and back, with power factor, efficiency and the breaker check.
• Resistor color codeBands in, ohms out — plus the range the tolerance band really allows and the reading a misread ring would give.
• Breaker sizeThe standard rating above your design current — and whether the cable behind it can carry that rating at all.