Electrical Calculators
Fast, accurate calculators for electronics hobbyists, students, electricians and anyone wiring a solar setup, camper van or Arduino project. Enter your values and get instant results with the formula shown, so you can check the math yourself.
10 free tools
All 10 electrical calculators
Ohm's Law Calculator
Enter any two of V, I and R to get the third, plus power.
Electrical Power Calculator
Convert between watts, volts, amps and ohms, including 3-phase.
Resistor Color Code Calculator
Decode 4, 5 and 6 band resistors, or find the bands for a value.
LED Resistor Calculator
Pick the right series resistor and wattage for any LED.
Series & Parallel Resistor Calculator
Total resistance of any number of resistors in series or parallel.
Voltage Drop Calculator
Check cable voltage drop and find the right wire size.
AWG to mm² Wire Gauge Converter
Convert AWG ↔ mm² and diameter, with a full gauge chart.
Battery Runtime Calculator
How long a battery lasts, or what size you need.
Capacitor Code Calculator
Decode codes like 104 or 4n7 into pF, nF and µF.
kWh to Joules Energy Converter
Convert kWh, J, Wh, kcal, BTU, therms and more.
Calculators for every step of a project
Start with the basics, Ohm's law and electrical power, then pick components: read a resistor color code, size an LED resistor, combine resistors in series or parallel and decode capacitor markings.
For wiring and power systems, check voltage drop over long cables, convert AWG to mm², estimate battery runtime and convert between kWh, joules and other energy units.