Electrical calculators
Voltage drop, Ohm’s law, motor amps, kVA, derating, conduit fill and wire resistance — the arithmetic, with the code values typed from your own book. Every one works in feet and inches or in metric — flip the switch at the top and the numbers you have typed convert with it.
8 tools
- Voltage drop volts & % lost over a cable run
- Ohm's law volts, amps, ohms & watts from any two
- Motor amps running current from horsepower
- kVA apparent power & amps, 1 or 3 phase
- Conductor derating corrected ampacity for heat & bundling
- Conduit fill fill % against the limit from your code book
- Wire resistance ohms of a run from size, length & resistivity
- Electricity cost kWh and running cost per day, month & year
Nothing in this drawer matches. Try the full index, which searches every tool.
Which one do I need?
The arithmetic of an electrical job. Anything a code sets — ampacities, fill limits, correction factors — you type from your own code book; the calculator never supplies a table value.
- Volts lost over a long run? Voltage drop calculator →
- Volts, amps, ohms or watts from two knowns? Ohm's law calculator →
- Running current of a motor? Motor amps calculator →
- Transformer or generator kVA? kVA calculator →
- How full is the conduit? Conduit fill calculator →
- Resistance of a run of wire? Wire resistance calculator →
The other drawers
- Concrete & masonry
- Framing & carpentry
- Site & landscape
- Finishes & interior
- Measure & layout
- Plumbing & HVAC
- Shop & equipment
- Conversions
- Every tool
Spot something wrong on this page? Report it
Thanks — your report was sent.
That didn’t send. Please try again later.
Calculators that fit your work — by email, optional
Drop your email and tick the box: at most one short note every two weeks with calculators related to the ones you use — here and on bentright.com and sparkytools.net. One list across the three, one-click out, and nothing is sent until you confirm from your inbox.