Electrical calculator

Ohm’s Law Calculator

Enter two known values to solve voltage, current, resistance, and power for a simple resistive circuit.

Solve voltage, current, resistance, and power

Enter any supported pair of known electrical values. The calculator applies Ohm’s law and the electrical power relationship to solve the remaining two quantities for a simple resistive DC circuit.

Worked example

With 12 volts across a 6-ohm resistance, current is 12 ÷ 6 = 2 amperes. Power is 12 × 2 = 24 watts. Entering any of those supported pairs returns the same ideal-circuit relationship.

When this model applies

• Use it for an ideal or approximately resistive DC load under steady conditions.
• Real components can change resistance with temperature and may have tolerances.
• AC circuits with inductance, capacitance, phase angle, or changing waveforms require impedance and power-factor analysis.
• Do not select wire, fuses, breakers, or protection devices from a single ideal calculation. Follow applicable codes and manufacturer instructions.

Electrical work can cause shock, fire, or equipment damage. De-energize safely and use a qualified electrician where required.

Frequently asked questions

What is one ohm?

An ohm is the resistance that permits one ampere of current when one volt is applied, expressed by the relationship 1 Ω = 1 V/A.

Can I enter zero?

The calculator requires positive inputs because several supported arrangements involve division. A true zero-resistance or zero-load case also falls outside this simple practical model.

Does this work for household AC wiring?

It may illustrate a purely resistive relationship, but household circuits involve safety rules, protective devices, conductor limits, and sometimes reactive loads. Use the appropriate AC method and electrical code.

How to get a dependable result

• Use measurements from the same trip, billing period, or planning scenario.
• Keep units consistent and enter positive numbers unless the field explicitly allows zero.
• Treat the result as an estimate. Real-world conditions, rounding, equipment efficiency, and changing prices can affect the final amount.

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Sources and review notes

Unit relationships and Ohm’s law are referenced to the National Institute of Standards and Technology SI electrical-unit guidance.

Last reviewed September 2026. This calculator provides an estimate for planning and education; it is not a substitute for a manufacturer specification, professional inspection, or safety advice.