Electrical Calculator

Ohm's Law, power calculations, and electrical unit conversions

Ohm's Law

Power

Resistors

V = I × R

Enter any two values to calculate the third

Voltage (V)

Current (A)

Resistance (Ω)

Voltage (V)

Current (A)

Resistance (Ω)

Power (W)

P = V × I

Calculate power, energy consumption, and cost

Power (Watts)

Hours of Use

Rate ($/kWh)

kWh Used

Cost

Amps @ 120V

Amps @ 240V

Calculate total resistance for series and parallel resistor configurations

R1 (Ω)

R2 (Ω)

R3 (Ω) — optional

R4 (Ω) — optional

Series Total (Ω)

Parallel Total (Ω)

V = I × R. Voltage equals current times resistance. This is the fundamental relationship in electrical circuits. Know any two, calculate the third.

Series: R_total = R1 + R2 + ... (resistances add up). Parallel: 1/R_total = 1/R1 + 1/R2 + ... (total is always less than smallest).

P = V × I = I²R = V²/R. Power in watts tells you energy use per second. 1 kWh = 1000W running for 1 hour.