Engineering
The Ohm's Law calculator solves electrical relationships between voltage, current, resistance, and power.
Calculator
Enter any two known positive values. Leave unknown fields blank.
Derived voltage, current, resistance, and power update live from the known values.
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Trust note
Use this result as a practical estimate. Real-world conditions, local rules, measurement tolerance, and changing inputs can affect the final outcome.
V = I x R, P = V x I
Ohm's law states that voltage equals current multiplied by resistance. Power can be derived from voltage and current.
Assumptions
Avoid mistakes
Follow the reasoning, not only the final number.
Choose the value you want to calculate.
Starting with clearly defined values and units prevents the most common calculation errors.
Enter two known electrical values.
This step transforms the known values into the form required by the formula.
Apply the relevant Ohm's law or power formula.
This step transforms the known values into the form required by the formula.
Review the result and related derived values.
Compare the result with your real-world goal, such as electrical projects.
Worked example
Voltage is 20 V and power is 40 W.
Calculator guide
Calculate voltage, current, resistance, and power from Ohm's law relationships. This page includes an interactive calculator, concise formula notes, worked examples, FAQs, related calculators, and practical guidance you can revisit whenever needed.
References
Last checked: 2026-06-25 | Next review: 2026-12-25
Last checked: 2026-06-25 | Next review: 2026-12-25
We work hard to keep every calculator accurate and useful. If you notice a calculation error, missing option, or unclear explanation, please let us know so we can review and correct it promptly.
Usage information loads after the calculator is ready.
FAQ
You can calculate voltage, current, resistance, and power when enough related values are known.
Yes. It is useful for quick educational and hobby electronics estimates.
Ohm's law states that voltage equals current multiplied by resistance: V = I x R.
It can solve voltage, current, resistance, and power when enough related values are known.
Use volts for voltage, amps for current, ohms for resistance, and watts for power.
Yes. Power can be calculated from voltage and current, or from related Ohm's law forms.
Use it as an educational estimate only. Real electrical work requires safety rules, ratings, and qualified guidance.
Component tolerance, heat, AC behavior, wiring resistance, and measurement error can change real circuit behavior.
It works for simple resistive relationships. AC circuits with impedance, phase, and frequency need more detailed analysis.
Zero resistance creates a short-circuit condition in the simple model and is not a valid practical input for current calculations.
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