Signal-to-noise ratio (SNR) measures how much stronger the desired signal is compared to background noise. Expressed in decibels: higher dB = cleaner signal. SNR applies to RF systems, audio amplifiers, ADC measurements, imaging sensors, and any system where noise degrades measurement quality.
SNR Calculator
Enter signal and noise values to calculate SNR.
SNR Quality Reference
How to Use the Signal-to-Noise Ratio Calculator
This SNR calculator computes signal-to-noise ratio in dB from power (mW/W) or voltage (mV/V) measurements. Select the measurement type, enter signal and noise values, and get SNR in dB with quality interpretation.
Power vs Voltage SNR
SNR for power: SNR(dB) = 10 × log10(P_signal / P_noise). SNR for voltage: SNR(dB) = 20 × log10(V_signal / V_noise). The factor of 20 vs 10 comes from power ∝ V². Always use the correct formula for your measurement — using power formula on voltage gives half the correct dB value.
SNR in Practice
WiFi: minimum 25 dB for reliable data transfer. Audio ADC: 80–120 dB for quality recording. 16-bit audio theoretical SNR: 98 dB. 24-bit audio: 144 dB (theoretical). Mobile phone audio: 80–100 dB. Medical ultrasound: 40–60 dB. Radar systems: often require positive SNR as low as -10 dB with signal processing.
Improving SNR
Signal amplification, bandwidth reduction (narrower filter = less noise), shielding, differential signaling, and averaging all improve SNR. Averaging N samples reduces noise by √N (3 dB improvement per 2× more samples). Doubling signal power adds 3 dB. Professional ADCs and amplifiers specify SNR in their datasheets.
FAQ
Is this SNR calculator free?
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What is signal-to-noise ratio (SNR)?
SNR measures the ratio of desired signal power to background noise power. Higher SNR = cleaner signal. Expressed in dB: SNR (dB) = 10 × log10(P_signal / P_noise) for power, or 20 × log10(V_signal / V_noise) for voltage. A 0 dB SNR means signal equals noise.
What is a good SNR value?
Very excellent: above 40 dB. Good: 25–40 dB. Acceptable: 10–25 dB. Poor: below 10 dB. Context matters: audio requires 50–70 dB+ for high quality. WiFi needs 25 dB+ for reliable data. Medical imaging may require 40–60 dB. Broadcast audio: 70+ dB.
Why is SNR calculated differently for power vs voltage?
Power ∝ V². When taking the log: 10 × log10(P) = 10 × log10(V²) = 20 × log10(V). So the factor is 10 for power ratios and 20 for voltage ratios. Using the wrong factor by 2× gives incorrect results — always specify whether you're measuring power or voltage.
What is noise floor?
Noise floor is the minimum detectable signal level — the level at which noise obscures the signal. Thermal noise (Johnson noise) sets the fundamental floor: P_noise = k × T × B, where k is Boltzmann's constant, T is temperature in Kelvin, and B is bandwidth. At room temperature and 1Hz bandwidth, thermal noise is about -174 dBm/Hz.
How do I improve SNR in my circuit?
Lower noise: use low-noise op-amps, shielding, star grounding, decoupling capacitors. Increase signal: amplify before filtering (signal+noise, but dominated by signal). Reduce bandwidth: filtering removes noise outside the signal band. Averaging: N measurements reduces noise by √N.