SNR Calculator Formula

Understand the math behind the snr calculator. Each variable explained with a worked example.

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Formulas Used

SNR

snr_db = 10 * log10(signal_power_mw / noise_power_mw)

SNR (linear)

snr_linear = signal_power_mw / noise_power_mw

Noise as % of Signal

noise_fraction_pct = noise_power_mw / signal_power_mw * 100

Variables

VariableDescriptionDefault
signal_power_mwSignal Power(mW)100
noise_power_mwNoise Power(mW)0.1

How It Works

Signal-to-Noise Ratio

SNR compares the level of a desired signal to the background noise level. Higher SNR means a cleaner signal.

Formula

SNR (dB) = 10 x log10(P_signal / P_noise)

For voltage measurements: SNR (dB) = 20 x log10(V_signal / V_noise)

Reference Points

  • 60+ dB: Excellent (hi-fi audio)
  • 40-60 dB: Good (voice communication)
  • 20-40 dB: Fair (some degradation)
  • < 20 dB: Poor (significant noise)

    • Worked Example

    Signal power of 100 mW with noise power of 0.1 mW.

    signal_power_mw = 100noise_power_mw = 0.1
    1. 01SNR linear: 100 / 0.1 = 1000
    2. 02SNR dB: 10 x log10(1000) = 30.0 dB
    3. 03Noise fraction: 0.1 / 100 x 100 = 0.1%

    Ready to run the numbers?

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