The 120 volts in your wall outlet is a quiet fiction — the peaks actually hit 170 volts. AC voltage swings in a sine wave, and the RMS (root-mean-square) value is the equivalent steady voltage that would deliver the same power: for a sine wave, V_rms = V_peak × 0.7071. Your outlet's 120 V is RMS; the 170 V peak is what the insulation and the surge protector must survive. Audio amplifiers, oscilloscopes, and multimeters all speak RMS because power cares about the average of the squares, not the tip of the wave.

This calculator converts peak to RMS. Type the waveform's peak voltage into Variable A — 170 for US mains — and the sine-wave factor 0.7071 into Variable B; the Result box gives the RMS voltage. A home-theater enthusiast in Denver checking a 40-volt-peak amplifier output, for instance, enters 40 in Variable A and reads about 28.3 V RMS — the number that, squared and divided by the speaker's 8 ohms, gives the real 100-watt rating. Square waves and triangle waves use different factors (1.0 and 0.577), so confirm your waveform is sinusoidal before trusting the 0.7071.

With the pre-filled defaults — Variable A 10, Variable B 5 — the Waveform Calculator returns Result 50.0000. Change any input and those results update instantly, so you can see exactly how each number you enter moves the answer.