Electrical guide
Understanding Volts, Amps, Watts, and Ohms
Electrical planning often starts with simple relationships, but it is important to know when those relationships stop being enough.
The simple relationship
For basic resistive calculations, watts equals volts times amps. Ohm's Law connects voltage, current, and resistance.
Phase and power factor can change current
AC loads may need power factor and phase information. Three-phase kW-to-amps calculations use a different formula than single-phase loads.
Load current is not final circuit design
Breaker, conductor, continuous-load, temperature, and installation rules can all change final circuit requirements.
Use the right calculator for the question
Use watts/amps/volts for simple conversions, Ohm's Law for resistance relationships, and kW-to-amps when phase and power factor matter.
Related Calculators
Watts Amps Volts Calculator
Solve the missing value from watts, amps, and volts.
Ohm's Law Calculator
Solve voltage, current, resistance, and power relationships.
Kilowatts to Amps Calculator
Estimate current from kW, voltage, phase, and power factor.
How to use this guidance
Use guides to understand calculator assumptions and next checks. Final design and installation decisions should still follow local requirements, manufacturer data, and qualified professional review where required. See how BuildCalcTools calculators work.