Harmonic Distortion Calculator
Total Harmonic Distortion (THD) measures how much a voltage or current waveform deviates from a pure sine wave because of harmonic frequencies injected by non-linear loads. This calculator takes the individual magnitudes of the 3rd, 5th, 7th, 9th, and 11th harmonics as a percentage of the fundamental (60 Hz) — as reported by a power quality meter or analyzer — and reports the combined THD, flagged against the commonly cited 5% IEEE 519 general guideline. High harmonic distortion is typical downstream of unmitigated VFDs, UPS systems, and other non-linear loads; for two related measures that pair naturally with a harmonic assessment, see our Variable Frequency Drive Savings Calculator and Power Factor Correction Calculator.
Magnitude of the 3rd harmonic as a percentage of the fundamental (60 Hz) magnitude.
Magnitude of the 5th harmonic as a percentage of the fundamental (60 Hz) magnitude.
Magnitude of the 7th harmonic as a percentage of the fundamental (60 Hz) magnitude.
Magnitude of the 9th harmonic as a percentage of the fundamental (60 Hz) magnitude.
Magnitude of the 11th harmonic as a percentage of the fundamental (60 Hz) magnitude.
Enter individual harmonic magnitudes as a percentage of the fundamental (60 Hz) magnitude, as reported by a power quality meter or analyzer.
High — likely exceeds IEEE 519 limits, mitigation may be needed
IEEE 519 actual limits vary by voltage level and system short-circuit ratio (a more detailed table-based standard, not a single flat number). The 5% figure used here is the commonly cited general guideline for voltage THD at the point of common coupling for typical systems — consult IEEE 519-2022 directly or a power quality engineer for your system’s specific applicable limit.
Results update live as you type. For planning and field-check estimates — always verify against applicable standards and equipment ratings.
How we calculate this →A THD of 19.3% is well above the commonly cited 5% general guideline in IEEE 519 for voltage distortion at the point of common coupling — a level like this is typical downstream of unmitigated VFDs, UPS systems, and other non-linear loads without harmonic filtering. High harmonic distortion isn't just a power-quality compliance issue — it increases losses and heating in transformers and motors, can trip sensitive electronic equipment, and may result in utility penalties or interconnection requirements for mitigation equipment like harmonic filters or 12-pulse/18-pulse drives.
How Total Harmonic Distortion is calculated
This calculator combines five individual harmonic magnitudes into a single Total Harmonic Distortion figure tied to five inputs: the 3rd, 5th, 7th, 9th, and 11th harmonic magnitudes, each expressed as a percentage of the fundamental (60 Hz) magnitude. One quantity ties the calculation together.
Total Harmonic Distortion, THD (%) = √(3rd Harmonic (%)² + 5th Harmonic (%)² + 7th Harmonic (%)² + 9th Harmonic (%)² + 11th Harmonic (%)²). THD is the root-sum-of-squares of the individual harmonic magnitudes — each harmonic contributes in quadrature, so two equal-magnitude harmonics combine to √(2) times one of them, not twice. At the default magnitudes (3rd 15%, 5th 10%, 7th 6%, 9th 3%, 11th 2%), that is √(15² + 10² + 6² + 3² + 2²) = √(225 + 100 + 36 + 9 + 4) = √374 = 19.34%. The result is then flagged against the commonly cited 5% IEEE 519 general guideline: a THD of 19.34% is well above that guideline and is flagged as high, likely exceeding IEEE 519 limits.
The crucial caveat on the standard itself: IEEE 519-2022 does not set a single flat THD limit. Its voltage distortion limits vary by voltage level (low-voltage, medium-voltage, high-voltage systems) and by the system short-circuit ratio at the point of common coupling — a table-based standard, not one number. The 5% figure used here is the most commonly cited general guideline for voltage THD at the point of common coupling for typical systems, useful as a quick first-pass screen, but the actual applicable limit for a given facility should be checked against the full standard or with a power quality engineer. Two notes on the model. First, it captures only these five harmonics — real power quality analyzers report many more (up to the 50th), and a facility with significant harmonics above the 11th would have a higher true THD than this calculator shows. Second, it treats each harmonic magnitude as a fixed percentage of the fundamental; real harmonic spectra vary with load and operating conditions, so a single snapshot may not represent the worst case. Data sources: IEEE 519-2022 standard for harmonic distortion limits; power quality measurement methodology from IEC 61000-4-7; harmonic distortion data from industrial power quality audits and VFD/UPS manufacturer specifications; transformer and motor heating loss calculations from IEEE and NEMA standards; utility interconnection requirements for harmonic mitigation.