Calculator inputs
Interactive waveform graph
Use the selected waveform, frequency, phase, and cycle controls. The chart marks RMS and peak levels. Custom samples appear as entered.
Household voltage comparison
These values assume a clean sine wave. Nominal outlet voltage varies by location. Actual measurements can differ from the listed supply.
| RMS voltage | Peak voltage | Peak-to-peak voltage |
|---|---|---|
| 100.00 V | 141.42 V | 282.84 V |
| 110.00 V | 155.56 V | 311.13 V |
| 115.00 V | 162.63 V | 325.27 V |
| 120.00 V | 169.71 V | 339.41 V |
| 127.00 V | 179.61 V | 359.21 V |
| 220.00 V | 311.13 V | 622.25 V |
| 230.00 V | 325.27 V | 650.54 V |
| 240.00 V | 339.41 V | 678.82 V |
Formula used
| Calculation | Formula |
|---|---|
| Sine-wave RMS from peak | VRMS = Vpeak ÷ √2 |
| Sine-wave peak from RMS | Vpeak = VRMS × √2 |
| Peak-to-peak voltage | Vpp = 2 × Vpeak |
| Waveform samples | VRMS = √[(Σv²) ÷ n] |
| Period | T = 1 ÷ f |
| Angular frequency | ω = 2πf |
| Appliance current | I = P ÷ (V × PF) |
| Transformer voltage | Vs ÷ Vp = Ns ÷ Np |
How to use this calculator
- Select the required calculation mode.
- Choose the waveform shape.
- Enter voltage, frequency, and related values.
- Use a household preset when helpful.
- Press Calculate to view the result.
- Review formulas, steps, and chart output.
- Copy, print, or export the result.
Example calculations
| Example | Inputs | Result |
|---|---|---|
| 120 V household sine supply | 120 V RMS | 169.71 V peak and 339.41 V peak-to-peak |
| 230 V household sine supply | 230 V RMS | 325.27 V peak and 650.54 V peak-to-peak |
| Square waveform | 100 V peak | 100 V RMS |
| Triangle waveform | 100 V peak | 57.74 V RMS |
| Appliance current | 1500 W, 230 V, PF 0.9 | About 7.25 A |
Understanding RMS household voltage
RMS voltage represents the heating effect of alternating voltage. It allows practical comparisons with direct voltage. Household supply ratings normally use RMS values.
Peak voltage is higher than the displayed RMS rating. A 120 V sine supply reaches about 170 V. A 230 V supply reaches about 325 V.
Waveform shape changes the RMS relationship. Square waves retain their full peak as RMS. Triangle and sawtooth waves use a different factor.
Average-reading meters assume a predictable waveform. True-RMS meters evaluate distorted signals more accurately. Always follow the meter manufacturer’s safe operating limits.
Electrical safety notice
Household mains voltage can cause severe injury or death. Never probe live circuits without proper training. Use correctly rated equipment and protective procedures.
This calculator provides theoretical estimates only. Electrical installations must follow applicable rules. Qualified electricians should handle mains wiring and repairs.
Frequently asked questions
What does RMS voltage mean?
RMS expresses an AC voltage by its equivalent heating effect. It provides a useful comparison with DC voltage.
Why is household voltage stated as RMS?
RMS relates directly to power in resistive loads. That makes equipment ratings easier to compare.
What is the peak of 120 V RMS?
A clean sine wave reaches about 169.71 V peak. Its peak-to-peak value is about 339.41 V.
What is the peak of 230 V RMS?
A clean sine wave reaches about 325.27 V peak. Its peak-to-peak value is about 650.54 V.
Does frequency change RMS voltage?
Frequency does not change RMS for a fixed ideal waveform amplitude. It changes period and angular frequency.
Does waveform shape affect RMS?
Yes. Sine, square, triangle, and sawtooth waves have different RMS factors.
What is a true-RMS meter?
A true-RMS meter calculates RMS from the measured waveform. It handles many distorted waveforms better.
Why can measured outlet voltage vary?
Supply regulation, load, wiring losses, and local standards affect readings. Small changes are often expected.
What is crest factor?
Crest factor equals peak voltage divided by RMS voltage. A sine wave has about 1.414 crest factor.
Can this calculator estimate appliance current?
Yes. It uses voltage, real power, and power factor. Real devices may also draw startup current.
Can this replace an electrician or meter?
No. It is an educational estimation tool. Use qualified professionals and correctly rated instruments.