Total Harmonic Distortion Calculator

Total Harmonic Distortion (THD) measures how much an electrical signal is corrupted by unwanted frequency components — a critical quality metric in audio, power, and electronics engineering. Enter your Fundamental Voltage (V1) and any harmonic components (V2–V5), then select a Calculation Method (Voltage or Power) to get your Total Harmonic Distortion percentage. Secondary outputs include THD in decibels, Distortion Factor, and Total Harmonics RMS voltage. Also try the calculate Phase Noise to Jitter RMS Phase Jitter.

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The amplitude of the fundamental frequency component

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Amplitude of the second harmonic component

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Amplitude of the third harmonic component

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Amplitude of the fourth harmonic component

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Amplitude of the fifth harmonic component

Choose whether to calculate based on voltage or power values

Results

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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Results Table

What is Total Harmonic Distortion (THD)?

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. See also our calculate Rise Time / Fall Time.

Why is THD important in electrical and audio systems?

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.

How is THD calculated from harmonic components?

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. You might also find our Signal-to-Noise Ratio (SNR) Calculator useful.

What is the difference between THD in percentage and dB?

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.

What are acceptable THD levels for different applications?

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.

How can I reduce THD in my system?

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.