RMS Voltage Calculator — Peak & Vpp (Free)

Convert Vrms, Vpeak, and peak-to-peak for sine waves

Target Variable

Required Parameters

RMS voltage

Waiting for input data...

Ad Placement

Sidebar Adaptive Ad Slot

Quick Answer

For a sine wave, Vpeak = Vrms × √2 and Vpp = 2 × Vpeak. 120 Vrms is 169.7 V peak and 339.4 V peak-to-peak. Vrms = Vpeak / √2.

Documentation

RMS Voltage Calculator

Convert RMS, peak, and peak-to-peak voltage for a sine wave. Mains and most DMM readings are RMS; oscilloscopes usually show peak or Vpp.

Quick start: Enter 120 Vrms → 169.7 V peak, 339.4 Vpp. Use the other modes to go from peak or Vpp back to RMS.

RMS formulas (sine)

Find	Formula
Peak from RMS	Vpeak = Vrms × √2
Vpp from RMS	Vpp = 2√2 × Vrms
RMS from peak	Vrms = Vpeak / √2
RMS from Vpp	Vrms = Vpp / (2√2)

Common values

Vrms	Vpeak	Vpp	Typical
120 V	169.7 V	339.4 V	US mains
230 V	325.3 V	650.5 V	EU mains
5 V	7.07 V	14.14 V	5 Vrms test tone
1 V	1.414 V	2.828 V	0 dBV

Peak vs peak-to-peak vs RMS

RMS — heating equivalent; use this in P = V × I
Peak — 0 to maximum
Peak-to-peak — negative peak to positive peak (2 × peak on a sine)

Do not use peak voltage in a power calculation or you will overstate power.

Related tools

Design Notes

RMS (root-mean-square) is the DC-equivalent heating value of an AC waveform. Mains, most DMMs, and power ratings quote RMS. Oscilloscopes often show peak or peak-to-peak. These ratios assume a pure sine wave. Square waves have Vrms = Vpeak; triangle waves use √3 instead of √2.

Common Mistakes

1
Using peak voltage in P = V × I for AC mains. Use Vrms or you will overstate power by √2.
2
Confusing peak with peak-to-peak. Vpp is twice the peak for a symmetrical sine.
3
Applying √2 to non-sine waveforms. The crest factor depends on the shape.

Engineering Handbox

1. Vpeak = 120 × √2 = 169.71 V 2. Vpp = 2 × 169.71 = 339.41 V

Verification120 Vrms (US mains) is 169.7 V peak and 339.4 V peak-to-peak.

Knowledge Base

What is RMS voltage?

RMS (root-mean-square) is the DC-equivalent heating value of an AC waveform. A 120 Vrms sine dissipates the same power in a resistor as 120 V DC. Mains, most DMMs, and power ratings are RMS unless labeled peak.

How do I convert RMS to peak?

For a sine wave: Vpeak = Vrms × √2 ≈ Vrms × 1.414. 120 Vrms → 169.7 V peak. 230 Vrms → 325.3 V peak.

How do I convert peak-to-peak to RMS?

Vrms = Vpp / (2√2) ≈ Vpp / 2.828. A scope trace that is 10 Vpp is 3.536 Vrms (sine). Peak is half of Vpp on a symmetrical wave.

What is the difference between peak and peak-to-peak?

Peak is from 0 V to the maximum. Peak-to-peak is from the negative peak to the positive peak — twice the peak for a symmetrical sine. Oscilloscopes usually display Vpp; power math uses Vrms.

Do these formulas work for square or triangle waves?

No. A square wave has Vrms = Vpeak. A triangle wave uses Vrms = Vpeak / √3. This calculator is for sinusoids — the waveform on AC mains and most signal generators in sine mode.

Should I use RMS or peak for power?

Use RMS: P = Vrms × Irms (resistive). Using peak overstates power by a factor of 2 for a sine (because P ∝ V² and Vpeak² = 2 × Vrms²).

Related Engineering Tools

basic circuit