Calculate voltage, current, resistance and electrical power using Ohm's Law. Enter any two known electrical values and this calculator determines the remaining values using the fundamental relationships between voltage, current, resistance and power.
Ohm's Law describes the relationship between voltage, current and resistance in a resistive electrical circuit.
Ohm's Law is one of the fundamental relationships used in electrical and electronic circuit analysis. It connects voltage, current and resistance.
| Calculate | Formula | Description |
|---|---|---|
| Voltage |
V = I × R
|
Current multiplied by resistance. |
| Current |
I = V / R
|
Voltage divided by resistance. |
| Resistance |
R = V / I
|
Voltage divided by current. |
| Power |
P = V × I
|
Voltage multiplied by current. |
| Power |
P = I² × R
|
Current squared multiplied by resistance. |
| Power |
P = V² / R
|
Voltage squared divided by resistance. |
Select the electrical quantity you want to calculate. Enter the two known values and select Calculate. The calculator determines the unknown value using the appropriate Ohm's Law relationship.
Suppose a circuit has a voltage of 12 V and a resistance of 6 Ω.
The current is:
If a circuit has a voltage of 12 V and current of 2 A, resistance is:
Power describes the rate at which electrical energy is transferred or consumed. For a simple resistive circuit, power can be calculated from voltage and current:
The standard SI units used in Ohm's Law calculations are volts (V), amperes (A), and ohms (Ω). Electrical power is measured in watts (W).
Engineering calculations frequently use prefixes such as milli-, micro-, kilo- and mega-. When working with these values, make sure all quantities are converted consistently before applying the formulas.