Electrical Calculator — Ohm's Law
Calculate Voltage (V), Current (I), Resistance (R), and Power (P) using Ohm's Law. Enter any two known values to instantly find the remaining two.
Ohm's Law Calculator
Enter any 2 known values — the other 2 will be calculated using V = IR and P = VI.
Results
Enter 2 values and click Calculate
Ohm's Law Formulas
Ohm's Law describes the relationship between voltage, current, and resistance in an electrical circuit. Combined with the power formula, any two of the four quantities determine the other two.
Core Formulas:
- V = I × R — Voltage equals Current times Resistance
- I = V / R — Current equals Voltage divided by Resistance
- R = V / I — Resistance equals Voltage divided by Current
- P = V × I — Power equals Voltage times Current
- P = I² × R — Power from Current and Resistance
- P = V² / R — Power from Voltage and Resistance
Units:
- Voltage (V): Volts (V)
- Current (I): Amperes (A)
- Resistance (R): Ohms (Ω)
- Power (P): Watts (W)
Frequently Asked Questions
What is Ohm's law?
Ohm's law states that Voltage = Current × Resistance (V = I × R). It links the three fundamental electrical quantities and lets you find any one from the other two.
How are amps, volts, and ohms related?
Current in amps equals voltage in volts divided by resistance in ohms (I = V / R). Increasing voltage raises current; increasing resistance lowers it.
How do I calculate electrical power?
Power in watts equals voltage times current: P = V × I. A 120 V device drawing 2 A uses 240 watts.
What units does this tool convert?
It handles common electrical units and prefixes — volts, amperes, ohms, watts, and their milli/kilo multiples — for quick circuit calculations.