Harmonic Distortion Calculator
Enter the fundamental and selected harmonic RMS values to calculate THD and each listed harmonic as a percentage of the fundamental.
- Combined harmonic RMS
- RMS
- Total harmonic distortion
- %
- 2nd harmonic
- %
- 3rd harmonic
- %
- 5th harmonic
- %
- 7th harmonic
- %
Calculation details
- Calculation basis
- Power-quality boundary
Recent results
Formulas
- Combined harmonic RMS = square root(H2^2 + H3^2 + H5^2 + H7^2)
- THD percent = combined harmonic RMS / fundamental RMS x 100
- Individual harmonic percent = harmonic RMS / fundamental RMS x 100
Use this calculator
Estimate total harmonic distortion from a fundamental RMS value and selected harmonic RMS components.
Read the result
Review the calculated values with their displayed units and assumptions. The result is a planning aid for the stated inputs, not a final equipment or installation decision.
Check before final work
This harmonic distortion estimate includes only the harmonic orders entered. It does not replace instrument measurements, waveform analysis, utility requirements, equipment limits, filter design, neutral analysis, or a power-quality study.
FAQs
Does THD include the fundamental?
No. THD compares the RMS sum of the selected harmonic components with the fundamental RMS value.
Can this prove a system meets a harmonic limit?
No. The result depends on which harmonics are measured, where they are measured, instrument method, operating state, and the applicable equipment or utility limit.