Enter your Fundamental Voltage (V1) and up to five harmonic voltages (V2–V5) into the Total Harmonic Distortion Calculator, choose your Calculation Method, and get your THD percentage alongside THD in Decibels, Distortion Factor, and Total Harmonics (RMS) — everything you need to measure how cleanly your signal is behaving.
Total Harmonic Distortion
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THD in Decibels
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Distortion Factor
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Total Harmonics (RMS)
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Total Harmonic Distortion (THD) is a measurement of the harmonic distortion present in a signal. It's defined as the ratio of the sum of the powers of all harmonic components to the power of the fundamental frequency, typically expressed as a percentage.
THD is crucial because it directly affects signal quality and accuracy. In audio systems, lower THD means components produce more accurate sound reproduction. In electrical systems, high THD can cause equipment inefficiency, overheating, and interference.
THD is calculated by taking the square root of the sum of squares of all harmonic components, divided by the fundamental component. The formula is: THD = √(V₂² + V₃² + V₄² + ...) / V₁, where V₁ is the fundamental and V₂, V₃, etc. are harmonics.
THD percentage shows the distortion as a direct ratio, while dB (decibel) representation uses a logarithmic scale. The conversion formula is: THD(dB) = 20 × log₁₀(THD%). Decibel values are useful for comparing very small distortion levels.
Acceptable THD levels vary by application: High-end audio equipment typically requires THD < 0.1%, consumer audio devices usually accept THD < 1%, and power systems generally require THD < 5% for voltage and < 8% for current.
THD can be reduced by using linear amplifiers, proper filtering, adequate power supply regulation, impedance matching, and avoiding overdriving components. In power systems, harmonic filters and proper system design help minimize distortion.