Ohm's Law Calculator
Solve voltage, current, resistance and power from any two compatible known quantities.
INPUTS
Calculation parameters
Enter project values below. The result updates when you calculate.
V
A
Select two different known quantities. Units update with the selected quantities.
Result
READYELECTRICAL POWER— W
Voltage V—
Current I—
Resistance R—
Power P—
Equation used—
This calculator uses ideal Ohm’s-law relationships. Reactive AC circuits require impedance, phase angle and RMS treatment.
Verification required: Results are calculation aids and are not guaranteed to be error-free or suitable for a specific project. Independently verify inputs, outputs, applicable standards, manufacturer data and project requirements before design release, procurement or installation.
Method
The four quantities are linked by Ohm’s law and the power equations.
V = I · R
P = V · I = I²R = V²/R
P = V · I = I²R = V²/R
01 · SELECTChoose any two independent electrical quantities.
02 · SOLVEThe result panel now shows the equation used.
03 · LIMITFor AC reactive circuits use impedance and phase-angle methods instead.
Calculation method
V = I × R; P = V × I
Worked example
For 24 V and 12 Ω, current is 2 A and power is 48 W.
Frequently asked questions
Does this calculate reactive AC power?
No. These equations cover resistive relationships. AC impedance and reactive power require a different model.
Which standards should I use?
Use the edition adopted for your project and jurisdiction. See the standards library for the scope of IEC, UL and NEC references.
Continue the design check
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