Quick start
- Choose the pair of values you know.
- Enter the two values in the labels shown.
- Calculate to get the remaining circuit values.
Best uses
Start here if one of these sounds like your job. The examples below show which inputs matter most.
- Find resistance from voltage and current.
- Find current from voltage and resistance.
- Find voltage from current and resistance.
- Estimate power after the core values are known.
What this calculator is solving
The Ohms Law Calculator solves the basic resistor relationships. Enter two known values and it fills in voltage, current, resistance, and power.
Match each input label on the calculator to the real measurement, amount, rate, unit, or setting for your job.
The formula in plain language
In plain language: The calculator uses V = I x R and P = V x I after the missing voltage, current, or resistance value is solved. The examples on the page are there so you can compare your inputs with a worked example before copying the answer.
The example cards on the calculator page show a complete set of inputs and the kind of answer you should expect.
How to read the answer
Read the main result first. Then check the smaller lines for the totals, units, ranges, counts, or formula steps behind it.
- Voltage is electrical potential difference.
- Current is flow in amps.
- Resistance is ohms, and power is watts.
Common mistakes to avoid
If the answer looks strange, the most likely cause is a small input mismatch: a mixed unit, copied value, wrong mode, missing label, or result used for the wrong job.
- Do not use simple DC resistor math for every AC or reactive circuit.
- Do not ignore component power ratings and heat.
- Never test live circuits without proper training and equipment.
Research and references
These references help check the measurements, units, limits, or safety notes used in this guide.
Worked examples for Ohms Law Calculator
6 ohms and 24 W
12 V and 24 W
3 A and 27 W
FAQ in plain language
When should I use the Ohms Law Calculator?
Use it when your task matches one of these common needs: Find resistance from voltage and current. Find current from voltage and resistance. It works best when you already know the measurements, amounts, units, or options the page asks for.
What is the Ohms Law Calculator doing with my inputs?
In plain language: The calculator uses V = I x R and P = V x I after the missing voltage, current, or resistance value is solved. The examples on the page are there so you can compare your inputs with a worked example before copying the answer.
What do the main Ohms Law Calculator inputs mean?
Voltage V: electrical potential difference, measured in volts. Current A: electrical flow through the circuit, measured in amps. Resistance ohms: how much the component or circuit resists current flow. Power W: energy rate, calculated after voltage and current are known.
How should I read the Ohms Law Calculator answer?
Read the headline answer, then check the supporting lines and examples to understand how the calculator got there. If one input changes, rerun the tool and compare the new answer instead of guessing.
What should I double-check before trusting the answer?
This is simple DC or resistive-circuit math. AC circuits, impedance, heat, component ratings, and electrical safety require more care. Also check the unit, scale, mode, and result limit because small input changes can change the answer.
Why do I only enter two values?
Ohm law connects voltage, current, and resistance. If you know any valid pair, the calculator can solve the missing core value and then calculate power from voltage times current.
Does the site save what I enter?
No. The calculator runs in your browser tab. Your recent answers stay only on the page while you use it, and they are not sent to a server.
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Keep exploring
If this guide is close but not exact, these links keep you near the same kind of problem.
- Calculators Browse the full category for related tools that help with the same job.
- All free tools Search the complete Access Free Tools library by task, category, or tool name.
- All calculator and utility guides Find more plain-language examples, formulas, mistakes, and result explanations.
- Free calculator resources Start here when you are not sure which calculator page fits.
Privacy and copying results
Recent answers stay visible only while you work in the current browser tab. They are not sent to a server.
Use Copy answer when you want to save the inputs and result in notes, homework, a message, or a project list. Check the units, labels, and limits before copying.