RMS Voltage Calculator
Convert peak or peak-to-peak voltage to RMS for a sinusoidal wave. Vrms = Vpeak / √2. The default 170 V peak matches a 120 V RMS household sine. Informational, not wiring approval.
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How to use the RMS voltage calculator
- Enter peak voltage, or peak-to-peak, or RMS if you are solving the other forms.
- For a sine, peak is the maximum above zero. RMS is the heating-equivalent value.
- Read RMS, peak, and peak-to-peak together. The page assumes a pure sinusoid.
- Treat the numbers as textbook AC math. Nothing is uploaded.
RMS voltage
Sinusoidal AC amplitude
| RMS | Root-mean-square voltage, heating equivalent |
|---|---|
| Peak | Maximum instantaneous voltage above zero |
| Peak-to-peak | Full swing from negative peak to positive peak |
| Relation | Vpeak = Vrms × √2 for a sine |
| Household example | 120 V RMS is about 170 V peak on a US sine |
| Scope | Informational. Not wiring or code approval. |
RMS from peak on a sine
For a symmetric sine, Vrms = Vpeak / √2 and Vpeak = Vrms × √2. Peak-to-peak is 2 × Vpeak. The default 170 V peak gives about 120.208 V RMS. Meters labeled AC volts on a sine usually read RMS.
Peak and peak-to-peak
Peak is one half of the peak-to-peak span on a centered sine. Scope traces often show peak-to-peak directly. If you only know Vpp, peak is Vpp / 2 and RMS is Vpp / (2√2).
What multimeters report
True-RMS meters report the heating value for arbitrary wave shapes. This page assumes a sine so the √2 factor applies. Distorted waves need a true-RMS instrument, not this ideal formula alone.
Limits
Assumes a pure sinusoid with no DC offset. Square waves, rectified pulses, and three-phase line values need different treatment.
The formula runs in this tab. CZNull does not receive the numbers.
Informational only. Not wiring, code, or manufacturer approval. See the disclaimer.