Ohm
Ohm's Law Calculator takes a voltage in volts and current in amperes and returns the resistance (V divided by I) in ohms and the power (V times I) in watts.
What this calculator does
The Ohm estimates your result instantly from the values you enter, using standard science & engineering formulas. Ohm's Law Calculator takes a voltage in volts and current in amperes and returns the resistance (V divided by I) in ohms and the power (V times I) in watts. Calculations run in your browser, so nothing you type is sent to a server, and the output is an estimate rather than a certified or official figure.
Result
About Ohm
Provide a voltage and a current and this tool applies Ohm's Law to find resistance and electrical power.
Resistance is voltage divided by current, and power is voltage multiplied by current.
Formula & Mathematical Calculation
Resistance (Ω) = f(Voltage (V), Current (A))
Calculated according to standard science formulas implemented in the calculator core.
Calculation Example
For V = 12 V and I = 2 A:
R = 12 ÷ 2 = 6 Ω and P = 12 × 2 = 24 W.
Key Benefits
- Returns both resistance and power from one calculation
- Guards against a zero current that would divide by zero
- Accepts decimal voltage and current values
- Shows results rounded to four decimals with clear units
How to Use this Calculator
-
Enter voltage
Type the voltage in volts in the Voltage field. -
Enter current
Type the current in amperes in the Current field. -
Calculate
Select Calculate to apply Ohm's Law. -
Read results
Read Resistance in ohms and Power in watts in the result boxes.
Assumptions & Limitations
What the calculation assumes
- Every value you enter is treated as an exact, known amount.
- Any rate or interval you enter is assumed to hold for the whole period unless the form asks for it separately.
- Results use standard published formulas and account only for the values entered above.
- Rounding is applied for display; the underlying calculation uses your full precision.
- Results are returned in the same units you enter, unless the tool states the output unit.
What it does not cover
- Ohm produces a calculated result for reference and learning, not a certified or official measurement.
- Real-world outcomes differ when tolerances, rounding rules or local standards apply.
- Definitions and standards vary by region and change over time; verify the convention that applies to your case.
- Figures are only as accurate as the inputs you supply — check them before acting on the result.
- For work where the result carries real consequences, confirm it against an authoritative source.
Frequently Asked Questions
Free to use, no account needed. Calculations run in your browser, so nothing you type is sent to a server. Results are estimates — how we build and check our calculators.