Please enter all required values.
RESULTS
Input Parameters Specification
Voltage TypeSelect peak voltage, peak-to-peak voltage, or average voltage as the known input.
Input VoltageEnter voltage value with V, mV, or kV unit selection.
RMS VoltageEquivalent heating/effective AC voltage value.
Waveform AssumptionCalculation is based on sinusoidal waveform relationships.
Practical Operational Examples
Peak to RMS
Convert oscilloscope peak voltage into RMS voltage for AC analysis.
Peak-to-Peak to RMS
Convert signal generator or scope Vpp reading into RMS voltage.
Average to RMS
Use average voltage input for sine-wave average based RMS estimation.
High Voltage RMS
Use kV input when checking transformer, inverter or high-voltage AC waveform RMS values.
Diagrams & Theory
The diagram shows peak value, RMS value, average value, peak-to-peak value, half cycle, full cycle, and time period for an AC sine waveform.
Formulas & Mathematical Logic
If input is Peak Voltage: Vrms = Vp / sqrt(2).
If input is Peak-to-Peak Voltage: Vrms = Vpp / (2 × sqrt(2)).
If input is Average Voltage: Vrms = Vavg × PI / (2 × sqrt(2)).
Unit conversion: V = value, mV = value × 0.001, kV = value × 1000.
Step-by-Step Example
Example 1: input type = peak voltage, input voltage = 325 V.
Step 1: Input is already in volts, so voltage = 325 V.
Step 2: RMS voltage = 325 / sqrt(2) = 229.81 V.
Example 2: input type = peak-to-peak voltage, input voltage = 650 Vpp.
Step 1: RMS voltage = 650 / (2 × sqrt(2)).
Step 2: RMS voltage = 229.81 V, or 0.22981 kV.
How to Use This Calculator
Select the known input voltage type: peak, peak-to-peak, or average.
Enter the voltage value.
Select the input unit: V, mV, or kV.
Click Calculate to get RMS voltage in volts and kV.
Use the RMS result for AC power, heating, transformer, inverter, or waveform analysis.
About This Calculator
Convert peak, Vpp or average voltage into RMS voltage.
The CalcBoy RMS Voltage Calculator calculates RMS voltage from peak voltage, peak-to-peak voltage or average voltage using sine-wave relationships.
RMS voltage is the effective value of an AC waveform. It tells how much heating or equivalent DC effect the waveform can produce. This is why mains voltage, transformer ratings, inverter output and many AC specifications are normally expressed in RMS instead of peak voltage.
This calculator is useful when you have an oscilloscope peak reading, a signal generator Vpp value, or an average voltage value and need the matching RMS voltage. For a sine wave, peak voltage is divided by sqrt(2), while peak-to-peak voltage is divided by 2 × sqrt(2). The calculator also displays the result in kV for high-voltage waveform checks.
Use this tool for AC waveform analysis, rectifier work, transformer secondary checking, inverter testing, audio amplifier voltage swing, power electronics measurement and oscilloscope conversion. Real non-sine or distorted waveforms can have different RMS relationships, so waveform shape should always be checked before using sine-wave formulas for final design.
Best UseRMS voltage conversion from peak, Vpp or average input.
Supported InputsPeak voltage, peak-to-peak voltage, average voltage, V, mV and kV.
Helpful ForAC power, oscilloscopes, signal generators, transformers and inverters.
Design ReminderRMS is related to heating and effective power.
Tip: A 650 Vpp sine wave is about 230 V RMS. That is why oscilloscope Vpp readings can look much larger than a normal AC meter reading.
Frequently Asked Questions
What is RMS voltage?
RMS voltage is the effective AC voltage value that produces the same heating effect as an equivalent DC voltage.
How do I convert peak voltage to RMS?
For a sine wave, RMS voltage equals peak voltage divided by sqrt(2).
How do I convert Vpp to RMS?
For a sine wave, RMS voltage equals peak-to-peak voltage divided by 2 × sqrt(2).
Why is RMS voltage important?
RMS voltage is used for power, heating, transformer ratings, inverter output and many AC measurements.
Can I use this for non-sine waves?
The calculator uses sine-wave relationships. Non-sine waveforms need waveform-specific RMS formulas.
Does the calculator support kV?
Yes. You can enter kV and the calculator converts it internally to volts.
Related Calculators
Peak Voltage CalculatorConvert RMS, average or peak voltage into peak voltage.
Peak-to-Peak Voltage CalculatorCalculate Vpp from RMS, peak or average voltage.
RMS and Average CalculatorCalculate RMS and average values for common waveforms.
Form Factor and Crest Factor CalculatorAnalyze waveform form factor and crest factor.