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DIY Cost Tools

DIY Cost Tools

RMS and Peak Voltage Calculator

Convert RMS voltage to peak and peak-to-peak values for an ideal sine wave.

Use the units shown beside each field. Decimal and scientific notation are accepted for non-integer fields; blanks, commas, fractions and non-finite entries are rejected.

RMS voltage120 V
Peak voltage169.7056275 V
Peak-to-peak voltage339.411255 V
Average rectified voltage108.0379579 V

The displayed results apply to the default example. Enable JavaScript to calculate other inputs.

How to use this calculator

  1. Replace the example values with measurements or ratings for the exact vehicle, circuit, component or system.
  2. Keep every value in the labeled unit and use manufacturer data where available.
  3. Select Calculate, then review the result together with the limitations and safety notes.

Formula and method

For a sine wave, Vpeak = Vrms × √2; Vpp = 2 × Vpeak; average full-wave-rectified voltage = 2 × Vpeak ÷ π.

Calculations run in your browser. Results are hidden whenever an input changes or validation fails, preventing an older result from being mistaken for a new calculation.

Worked example

RMS voltage = 120 V. The calculator returns RMS voltage = 120 V; Peak voltage = 169.7056275 V; Peak-to-peak voltage = 339.411255 V; Average rectified voltage = 108.0379579 V.

The worked example uses the same defaults shown in the interface, allowing the formula and displayed result to be checked together.

Limitations and safety

These relationships apply only to an ideal sine wave. Distorted, pulsed, clipped or offset waveforms need waveform-specific RMS analysis.

This is an educational planning model. Confirm ratings, tolerances, code requirements and safe procedures with manufacturers and qualified professionals before purchasing, modifying, wiring or operating equipment.

Frequently asked questions

Is 120 V AC the peak voltage?

No. For an ideal 120 V RMS sine wave, the peak magnitude is about 169.7 V.

Why does the calculator reject my entry?

Each field shows its supported range. Whole-number fields reject decimals, and all fields reject blanks, words, comma-formatted numbers, fractions and non-finite values.

How should I use the displayed precision?

Keep extra digits while checking the calculation, then round to the precision supported by the measurements, component tolerances and published ratings.

Review notes and reference

Reviewed October 4, 2026. The formula and default example were checked together. The script was tested for defaults, input boundaries, invalid formats, condition-specific errors and recovery after an error. Reference: OSHA electrical safe-work requirements. Explanations and examples are original.

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