Signal-to-Noise Ratio (SNR) Calculator
By Santaji GadepatilinUpdated October 27, 2026
Signal-to-noise ratio compares the signal you want with the unwanted noise riding on it, usually in decibels. It sets how small a change you can reliably measure; see this signal-to-noise ratio guide, decibels in electronics and what signal integrity means.
How to use the signal-to-noise ratio calculator
Enter the RMS signal and RMS noise voltages (any matching unit). You get the SNR in dB, the power ratio and the equivalent ADC resolution (ENOB).
Signal-to-noise ratio formulas
SNR = 20 log₁₀(Vs ÷ Vn) = 10 log₁₀(Ps ÷ Pn)
ENOB = (SNR − 1.76) ÷ 6.02
SNR reference
| SNR | Voltage ratio | ENOB |
|---|---|---|
| 20 dB | 10 : 1 | 3.0 |
| 40 dB | 100 : 1 | 6.4 |
| 50 dB | 316 : 1 | 8.0 |
| 60 dB | 1,000 : 1 | 9.7 |
| 74 dB | 5,012 : 1 | 12.0 |
| 86 dB | 19,953 : 1 | 14.0 |
| 98 dB | 79,433 : 1 | 16.0 |
| 110 dB | 316,228 : 1 | 18.0 |
An ideal 12-bit ADC reaches 74 dB and an ideal 16-bit ADC 98 dB.
Sources of noise
| Noise | Cause | Remedy |
|---|---|---|
| Thermal (Johnson) | Random electron motion in resistors | Lower resistance, narrower bandwidth |
| Mains hum (50/60 Hz) | Magnetic and capacitive pickup | Twisted pairs, shielding, notch or integrating ADC |
| Switching noise | SMPS, VFDs | Layout, ferrites, filtering |
| Quantisation | ADC step size | More bits, dithering |
Thermal noise floor
A resistor’s noise voltage is √(4kTRB). A 10 kΩ resistor at 25 °C over 10 kHz bandwidth produces about 1.3 µV RMS.
Frequently asked questions
How do I calculate SNR in dB?
For voltages, SNR = 20 log₁₀(V_signal ÷ V_noise); for powers, SNR = 10 log₁₀(P_signal ÷ P_noise). Both give the same dB value.
What is a good SNR?
It depends on the application. Process instrumentation and audio aim for 60–100 dB; Wi-Fi works from about 20–25 dB; 10 dB is marginal for most signals.
What is ENOB?
The effective number of bits — the resolution of an ideal ADC with the same SNR. ENOB = (SINAD − 1.76) ÷ 6.02.
How can I improve SNR?
Increase the signal level early in the chain, shield and twist cables, filter out-of-band noise, use differential inputs and average multiple readings.