Total Harmonic Distortion (THD) Calculator

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Use "Individual harmonics" when you have spectrum analyzer or FFT readings for each harmonic order. Use "Total RMS method" when you have only the overall RMS and fundamental RMS from a multimeter.
RMS amplitude of the fundamental (first harmonic). Enter in any consistent unit: V, A, or a dimensionless scale.
RMS amplitude of the 2nd harmonic. Leave at 0 if not present.
RMS amplitude of the 3rd harmonic. The 3rd is the dominant distortion harmonic in most AC power systems.
THDPoor
6.325%

Total harmonic distortion as a percentage of the fundamental

THD-23.98dB
Harmonic RMS6.3246
H2 level5%
H3 level3%
H5 level2%
H7 level1%
6.325 %
Excellent<1Good1-3Acceptable3-5Poor5-8Unacceptable8+

THD is 6.325% (-24.0 dB) - rated Poor.

  • THD above 5% exceeds the IEEE 519 limit for standard industrial systems and indicates significant waveform distortion.

Next stepConsider passive harmonic filters, active power factor correction, or phase-shifting transformers to bring THD into compliance.

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