Calculate current, apparent power, continuous-load planning current, and a reference breaker from separate electrical loads.
Calculator
Electrical Load Results
Review the main result, supporting measurements, and calculation details.
Power and Current Analysis
Calculation Details
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How to calculate electrical load
Enter continuous and noncontinuous real power separately, then select DC, single-phase AC, or three-phase AC. For AC loads, enter power factor. The calculator reports actual current, apparent power, 125%-adjusted planning current, and a reference standard breaker.
single-phase amps = watts / (volts x power factor); three-phase amps = watts / (√3 x volts x power factor)
Electrical-load example
At 120 V single phase and power factor 1.0, 1,800 W continuous plus 600 W noncontinuous equals 2,400 W and 20 A actual current. Applying 125% only to the continuous portion produces 23.75 A of planning current and a 25 A reference breaker.
Watts, VA, and power factor
Watts measure real power. Volt-amperes measure apparent power. For AC loads below unity power factor, the same real power requires more current. DC calculations ignore the power-factor entry.
Panel and service limitations
This tool combines entered loads; it is not a residential service calculation. The US Department of Energy's panel-upgrade factsheet explains that electricians use nameplate loads and NEC demand methods rather than simply adding breaker ratings.
Frequently asked questions
What counts as continuous load?
A load expected to operate at maximum current for three hours or more is generally treated as continuous; confirm the applicable definition and equipment rule.
Does this include motor efficiency?
No. Enter electrical input watts, not mechanical output watts. Motors and HVAC equipment should be sized from nameplate and applicable rules.
Can I convert a single value?
Use the watts to amps calculator or amps to watts calculator for a simpler conversion.