Ohms Law Calculator
Calculate Ohms Law values for science, physics, chemistry, and engineering problems.
This Ohm's law calculator solves V = IR for voltage, current, or resistance - whichever value you're missing - the fundamental relationship describing how these three quantities interact in an electrical circuit.
Enter any two of voltage, current, and resistance, and the calculator solves for the third.
Worked Calculation Examples
| Scenario | Result | Calculation Step |
|---|---|---|
| Current 2 A, resistance 10 Ω | V = 20 V | V = 2 × 10 = 20 V. |
| Voltage 12 V, resistance 4 Ω, find current | I = 3 A | I = V ÷ R = 12 ÷ 4 = 3 A. |
Ohm's Law Formula
V = IR, where V is voltage (volts), I is current (amps), and R is resistance (ohms). Rearranged, I = V/R (current equals voltage divided by resistance) and R = V/I (resistance equals voltage divided by current) - all three forms describe the same underlying relationship.
How Voltage, Current, and Resistance Relate
For a fixed resistance, increasing voltage increases current proportionally - more electrical 'pressure' pushes more current through the same resistance. For a fixed voltage, increasing resistance decreases current, since resistance opposes the flow of current, similar to how a narrower pipe restricts water flow at the same pressure.
How to Use the Ohms Law Calculator
- Open the Ohms Law Calculator and enter the values requested in the input fields.
- Check the units, percentages, dates, or time periods before reading the answer.
- Review the instant result and adjust any value to compare another scenario.
- Use the formula, example, and FAQs below to understand how the ohms law calculator works.
Frequently Asked Questions
What is Ohm's law?
Ohm's law states that voltage equals current multiplied by resistance: V = IR, describing the relationship between these three quantities in an electrical circuit.
How do you find current using Ohm's law?
Rearrange the formula: current = voltage / resistance (I = V/R).
What happens to current if resistance increases?
If voltage stays constant, increasing resistance decreases current, since resistance opposes current flow - this is the inverse relationship shown by I = V/R.
How do I use this ohms law calculator?
Enter the known values, review the units or settings, and the calculator updates the result instantly. The formula and example on this page show how the answer is produced.
What does the Ohms Law Calculator calculate?
Calculate Ohms Law values for science, physics, chemistry, and engineering problems. It is designed for fast browser-based calculations without sign-up, downloads, or manual spreadsheet setup.
What formula does this ohms law use?
The formula is: V = I × R. German physicist Georg Ohm published this relationship in 1827, though his work was initially dismissed by much of the German scientific establishment as overly simplistic - it took years, and eventual recognition from the Royal Society in London, before Ohm's law became accepted as fundamental. The ohm (Ω), the SI unit of electrical resistance, was named in his honor in 1881, decades after his original, initially unappreciated discovery.
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Last updated: September 27, 2026.