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Vpp = 2 × Vpeak
Vpp = 2√2 × Vrms
Peak-to-peak voltage (Vpp) is the full swing of an alternating signal measured from its most negative point to its most positive point. For a pure sinusoidal waveform, Vpp equals exactly twice the peak voltage, or equivalently 2 times the square root of 2 (approximately 2.828) multiplied by the RMS voltage. This measurement is critical in electronics because it tells you the total voltage excursion a component must withstand. Oscilloscopes display Vpp directly, making it one of the easiest AC measurements to take, and it is essential for sizing capacitors, selecting transistor breakdown ratings, and designing amplifier circuits that must avoid clipping.
Identify whether you have the peak voltage (Vpeak), the RMS voltage (Vrms), or an oscilloscope reading. The conversion formula depends on which measurement you start with.
From peak voltage: Vpp = 2 x Vpeak. From RMS voltage: Vpp = 2 x 1.414 x Vrms. For example, a 120V RMS mains supply has a Vpp of approximately 339.4V.
The formulas above apply to sinusoidal waveforms only. For square waves, Vpp equals the full amplitude swing directly. For triangle or sawtooth waves, Vpp equals the full excursion from trough to crest.
Connect your oscilloscope probe to the signal, adjust the vertical scale so the waveform fills the screen, and use the built-in Vpp measurement or count the divisions from the lowest to highest points of the waveform.
Capacitors, transistors, and diodes must be rated above the peak-to-peak voltage they will experience. Using RMS values alone can lead to under-rated parts and failures.
In audio and RF engineering, knowing Vpp ensures amplifiers and transmission lines operate within their linear range, preventing distortion and clipping.
Rectifier circuits must handle the full peak-to-peak voltage of the AC input. Filter capacitor voltage ratings and diode PIV ratings depend directly on Vpp.
Reference table for standard AC mains and audio voltages showing the relationship between RMS, peak, and peak-to-peak values for sinusoidal waveforms.
| Application | Vrms | Vpeak | Vpp |
|---|---|---|---|
| US Mains (120V) | 120 V | 169.7 V | 339.4 V |
| EU Mains (230V) | 230 V | 325.3 V | 650.5 V |
| Japan Mains (100V) | 100 V | 141.4 V | 282.8 V |
| Line-Level Audio | 0.316 V | 0.447 V | 0.894 V |
| Professional Audio (+4 dBu) | 1.228 V | 1.736 V | 3.472 V |
| Telephone Ring Signal | 48 V | 67.9 V | 135.8 V |
| Low-Voltage Lighting (24V) | 24 V | 33.9 V | 67.9 V |
| Doorbell Transformer (16V) | 16 V | 22.6 V | 45.3 V |
No. Peak voltage is the maximum excursion from the zero line (center) of the waveform, while peak-to-peak voltage is the total swing from the most negative to the most positive point. For a symmetrical sine wave, Vpp is exactly twice the peak voltage.
Multimeters display RMS because it represents the equivalent DC value that would deliver the same power to a resistive load. RMS is more practical for power calculations, while Vpp is more useful for component voltage rating and signal analysis.
The relationship between RMS and Vpp depends on the waveform shape. The 2 times the square root of 2 factor only applies to pure sine waves. For square waves, Vpp = 2 x Vrms. For triangle waves, Vpp = 2 x the square root of 3 x Vrms. Always consider the waveform type when converting.
Set your oscilloscope to display at least one full cycle of the waveform. Use the vertical cursors or the automatic measurement function to find the distance from the lowest trough to the highest crest. Multiply the number of vertical divisions by the volts-per-division setting.
A pure DC signal has zero Vpp because it does not oscillate. However, real-world DC supplies have ripple, and the Vpp of that ripple indicates the quality of the power supply filtering. A well-filtered supply might have only millivolts of Vpp ripple.