Total Harmonic Distortion Calculator

Total Harmonic Distortion (THD) measures the ratio of the sum of the powers of all harmonic components to the power of the fundamental frequency. When evaluating audio or electronic circuits, engineers often express harmonic rejection or distortion metrics via attenuation in decibels (dB). The core formula linking attenuation to THD percentage is expressed as: attenuation = 20 * log10(THD / 100). By rearranging this logarithmic equation, you can easily convert an attenuation decibel value back into a precise distortion percentage to analyze system integrity.

Imagine you are testing an amplifier and measure an attenuation value of -40 dB for a specific harmonic product. To find the corresponding Total Harmonic Distortion percentage, we apply the inverse of our core formula. First, divide the attenuation by 20: -40 / 20 = -2. Next, raise 10 to the power of -2, which yields 0.01. Finally, multiply this result by 100 to convert it into a percentage, giving you a THD of 1.0%. This tells you that the harmonic distortion component is operating at one percent of the fundamental signal strength.

When working with harmonic distortion metrics, always verify whether your equipment measures attenuation in voltage ratios (using the standard 20 multiplier) or power ratios (which would use a 10 multiplier). Additionally, ensure your input baseline frequencies are stable to avoid skewed readings. Finally, cross-reference your calculated percentages with industry standards to determine if the equipment performance falls within acceptable operational thresholds.