RMS to Peak Converter
Enter an RMS value, choose the waveform (or custom crest factor), and calculate the peak and peak-to-peak values instantly.
Also: Peak-to-Peak = 2 × Peak
What This RMS to Peak Calculator Does
This tool converts an RMS (root mean square) value into its corresponding peak value, using the waveform's crest factor. It is useful for electronics, audio engineering, AC power analysis, and signal processing where you often need to move between effective values (RMS) and maximum instantaneous values (peak).
RMS vs Peak: Quick Explanation
RMS (Root Mean Square)
RMS represents the effective value of a varying signal. For voltage and current, RMS is the DC-equivalent value that would deliver the same power to a resistor. That is why household AC voltage ratings are usually provided in RMS values.
Peak Value
Peak is the highest instantaneous amplitude reached by the waveform. A signal can have the same RMS as another signal but a different peak, depending on waveform shape.
Crest Factor
Crest factor is the ratio between peak and RMS:
Crest Factor = Peak / RMS
Rearranging gives the conversion used by this calculator:
Peak = RMS × Crest Factor
Common Crest Factors
- Sine wave: √2 ≈ 1.4142
- Square wave: 1.0
- Triangle wave: √3 ≈ 1.7321
- Sawtooth wave: √3 ≈ 1.7321
Example Calculations
Example 1: AC Mains (Sine)
If RMS voltage is 120 V and the waveform is sinusoidal:
Peak = 120 × 1.4142 = 169.7 V
Peak-to-peak = 2 × 169.7 = 339.4 V
Example 2: Audio Signal
If an amplifier output is 10 Vrms (sine approximation):
Peak = 10 × 1.4142 = 14.142 V
This helps when selecting headroom, op-amp rails, and ADC input limits.
How to Use This Tool
- Enter your RMS value.
- Select the waveform type, or choose custom crest factor.
- Click Calculate.
- Read the peak and peak-to-peak results.
Practical Notes
- Always confirm the waveform shape before conversion.
- For non-ideal real-world signals, use measured crest factor if available.
- In power systems, reported nominal values are typically RMS.
- In oscilloscope work, you may directly observe peak and peak-to-peak values.
FAQ
Can I use this for current as well as voltage?
Yes. The same RMS-to-peak relationship works for current and other linear amplitude quantities.
Why is sine wave peak not equal to RMS?
Because RMS is an effective power-equivalent value, not the maximum instantaneous amplitude.
What if I know peak and need RMS?
Use: RMS = Peak / Crest Factor.