Physics

Instant, private, and free

RMS Voltage Calculator.

Calculate sinusoidal RMS voltage from peak voltage.

On-device calculationNo signup
01

Set your values

Results update as you type.

RMS voltage: 120.208153 V

RMS voltage

0.000000V

Results update automatically as you type.

Use Cases

AC Circuit Analysis

Determine the effective voltage of an AC supply for power calculations and equipment ratings.

Example: If a wall outlet has a peak voltage of 325 V, the RMS voltage is 230 V.

Audio Engineering

Convert peak signal levels to RMS to understand perceived loudness and set proper gain staging.

Example: A sine wave with a peak of 1 V has an RMS of 0.707 V.

Frequently Asked Questions

What is RMS voltage and why is it important?
RMS (Root Mean Square) voltage is the effective value of an AC voltage that produces the same heating effect as an equivalent DC voltage. It's crucial for power calculations and is the standard measure for AC voltages.
How is RMS voltage calculated from peak voltage?
For a sinusoidal waveform, RMS voltage equals the peak voltage divided by the square root of 2 (approximately 0.7071 times the peak). This calculator uses that formula.
Can I use this calculator for non-sinusoidal waveforms?
No, this calculator is specifically for sinusoidal waveforms. For other waveforms, the relationship between peak and RMS differs.

Tips & Common Mistakes

Tips

  • Ensure the peak voltage is measured from zero to the maximum positive or negative amplitude, not peak-to-peak.
  • For a sine wave, RMS is always about 70.7% of the peak value.
  • Use this calculator for quick conversions when designing or testing AC circuits.
  • Remember that this tool assumes a pure sinusoidal waveform; for other shapes, use a true RMS meter.

Common Mistakes to Avoid

  • Using peak-to-peak voltage instead of peak voltage. Peak-to-peak is twice the peak, so divide by 2 first.
  • Confusing RMS with average voltage. For a sine wave, average is 0.637 times peak, not 0.707.
  • Applying the formula to non-sinusoidal waveforms without adjustment.

Last updated: August 13, 2026