voltage and current
- Voltage
- 12 V
- Current
- 2 A
- Resistance
- 6 ohms
This is simple DC/resistive-circuit math. Real circuits can involve AC, impedance, heat, and safety limits.
Ohm's Law Calculator
Use this free Ohm's law calculator to solve voltage, current, resistance, and power from two known V, I, R, or P values.
Inputs explainedResult checksExample valuesRuns in your browser
Formula steps
- Use Ohm's law V = I x R to solve the missing core value.
- Use power P = V x I after voltage and current are known.
- Show voltage, current, resistance, and power together for checking.
Examples
Recent answers
Recent Ohm's law calculations will appear here.
This simple resistor math stays in your browser. Use proper electrical safety practices.
Inputs and recent answers stay in this browser tab and are not sent to a server.
How to use the Ohm's Law Calculator
- Choose the pair of known values you have: V and I, V and R, I and R, V and P, I and P, or R and P.
- Enter the two values and press Calculate circuit values.
- Review voltage, current, resistance, and power together.
- Use extra caution for live circuits, AC loads, heat, and component ratings.
What people use it for
Find resistance from voltage and current.
Find current from voltage and resistance.
Find voltage from current and resistance.
Find current and resistance from voltage and power.
Find voltage and resistance from current and power.
Check the watt result before comparing component ratings.
Quick examples
Voltage and current
12 V and 2 A6 ohms and 24 W
Current and resistance
2 A and 6 ohms12 V and 24 W
Voltage and resistance
9 V and 3 ohms3 A and 27 W
Voltage and power
12 V and 24 W2 A and 6 ohms
Current and power
2 A and 24 W12 V and 6 ohms
Resistance and power
6 ohms and 24 W12 V and 2 A
Need the guide or a nearby tool?
Need a slower walkthrough, a related calculator, or the full library? These links keep you close to the task you started.
- How to use the Ohm's Law CalculatorSee slower examples, input meanings, formula notes, result limits, and mistakes to avoid.
- CalculatorsBrowse related calculators and utilities in the same category.
- Electrical Calculator HubCompare this with the nearby tools and checks in the same job path.
- Calculator and utility guidesFind more guides that use real tool inputs and example numbers.
- All free toolsSearch every live tool, converter, calculator, AI helper, and browser utility.
Frequently asked questions
Plain-language answers about when to use the tool, what it does with your inputs, what to double-check, and how privacy works.
When should I use the Ohm's 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 two positive values from the same simple DC or resistive circuit.
What is the Ohm's Law Calculator doing with my inputs?
In plain language: The calculator uses V = I x R and P = V x I. Depending on the pair you choose, it can rearrange those relationships as I = V / R, R = V / I, P = V x I, and V = sqrt(P x R). 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 Ohm's 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 in watts, equal to voltage times current for this simple calculation.
How should I read the Ohm's 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. It is not a safety approval for live wiring, AC impedance, component heat, fuse sizing, battery limits, or code compliance. Also check that all values come from the same circuit, the mode matches the pair you know, and any real component can handle the calculated current, voltage, and power.
Why do I only enter two values?
Ohm's law connects voltage, current, and resistance, and power connects voltage and current. If you know any supported positive pair, the calculator can solve the remaining values.
Can I solve from power and one other value?
Yes. The visible modes include voltage and power, current and power, and resistance and power. For example, 12 V and 24 W gives 2 A and 6 ohms.
Why are zero or negative values rejected?
The page is built for simple positive circuit quantities. Zero resistance, zero current, or negative values can mean a different kind of circuit model, a short circuit, or an invalid entry for this quick calculator.
Can I use milliamps or kilohms?
Yes, but convert them first or stay consistent with the labels. For example, 500 mA is 0.5 A and 2 kOhm is 2,000 ohms. Mixing units without converting changes every answer.
Does this handle AC impedance?
No. AC circuits can involve impedance, phase angle, frequency, RMS values, and power factor. Use this page for simple DC or purely resistive examples only.
How should I use the watt result?
Treat watts as a heat and power-rating check. A calculated 24 W load needs parts, wiring, fuses, and power supplies rated for the real circuit, not just the math result.
Does the site save what I enter?
No. The calculator runs in your browser tab. Your recent Ohm's law answers stay only on the page while you use it, and they are not sent to a server.