Electrical Calculators

Free electrical calculators for watts, amps, volts, kWh, electricity cost, voltage drop, battery life, and wire sizing.

Calculate watts from volts and amps using P = V × I.

Calculate amps from watts and volts using I = P / V.

Calculate volts from watts and amps using V = P / I.

Calculate voltage, current, or resistance using Ohm's law.

Calculate kilowatt-hours from watts and usage time.

Calculate daily, monthly, and yearly electricity costs from device wattage and usage.

Calculate voltage drop in electrical wire based on gauge, length, and current.

Calculate battery runtime from capacity (mAh) and device consumption (mA).

Calculate how long a battery will last under load.

Recommend AWG wire gauge based on amperage and distance.

Decode resistor values from color bands.

Calculate resistor value needed for LED circuits.

Calculate resistance using Ohm's law or wire properties.

Calculate electrical power (P=VI, P=I²R, P=V²/R).

Estimate solar panels needed for your energy usage.

Calculate battery bank size for solar systems.

Calculate series and parallel resistance combinations.