Ohm's Law Calculator
Enter any two values -- the calculator finds the third, plus power
Results
Computed Value
Power
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Ohm's Law Calculator Formula
Solve for Voltage:
V = I × R
Solve for Current:
I = V / R
Solve for Resistance:
R = V / I
Power (always computed):
P = V × I
How to Use This Calculator
- Enter the values you know for two of the three fields (Voltage, Current, Resistance).
- Leave exactly one field blank -- that is the value the calculator will solve for.
- Click Calculate to find the missing value plus power in watts.
- Copy the URL to share your result -- the link auto-fills the inputs and calculates on load.
Frequently Asked Questions
What is Ohm's Law?
Ohm's Law states that the voltage across a conductor is directly proportional to the current flowing through it, with resistance as the constant of proportionality: V = I × R. It is one of the fundamental laws in electrical engineering and physics.
What units does this calculator use?
This calculator uses SI base units: volts (V) for voltage, amperes (A) for current, ohms for resistance, and watts (W) for power.
Why must all inputs be greater than zero?
Negative and zero values would produce physically meaningless or undefined results for basic DC circuit analysis. Convert any negative voltage or current to its magnitude before calculating.
How are results formatted?
Results are displayed with up to 4 decimal places. Very small values (below 0.001) use up to 4 significant digits to avoid displaying as zero.
What is electrical power and how is it calculated?
Electrical power (measured in watts) is the rate at which electrical energy is consumed or produced. It can be calculated as P = V × I, P = I²R, or P = V²/R. This calculator derives power automatically from whichever two values you provide. For another physics calculator that solves for a missing variable, see our Bernoulli's equation calculator.
Can I share my calculation?
Yes. After clicking Calculate, the URL updates with your input values. Copy and share the URL to let anyone else see the same pre-filled form and result.