Signal-to-Noise Ratio Calculator · SNR in dB

Signal-to-Noise Ratio Calculator

Calculate SNR in dB from signal and noise levels in voltage or power

Quick preset

Inputs

Measurement type

Signal level

Noise level

SNR (dB) = 20 × log₁₀(signal ÷ noise) for voltage · SNR (dB) = 10 × log₁₀(signal ÷ noise) for power. Higher is better.

Quick examples

SNR Result

Signal-to-noise ratio

— dB

— — —

Linear ratio

— : 1

Noise figure

— dB

SNR in nepers

— Np

Signal-to-noise %

— %

SNR quality classes — what this means

SNR range	Quality	Typical applications

Reference — common SNR values by application

Application	Typical SNR	Quality	Notes

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Creator & Maintainer

Faiq Ur Rahman is a web designer, digital product developer, and founder of Toolraxy, a growing platform of web-based calculators and utility tools. He specializes in building structured, user-friendly tools focused on health, finance, productivity, and everyday problem-solving.

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Signal-to-Noise Ratio Calculator: Voltage, Power, and dB

This tool takes a signal level and a noise level, then returns the signal-to-noise ratio in decibels. Choose voltage or power mode. You’ll also see the linear ratio, noise figure, nepers, and the percentage of the total that’s signal. Eight presets cover common scenarios from bad WiFi to studio-grade audio. No sign-up, and the math runs in your browser.

A signal-to-noise ratio tells you how much stronger a signal is than the noise around it. It’s a core number in audio, radio, networking, and electronics. This calculator does the log math for you. Enter a signal level and a noise level, pick voltage or power, and you’ll get the SNR in decibels plus four related values. Engineers use it to check whether a link will work. Audio techs use it to compare gear. Students use it to check homework. The formula depends on whether you’re measuring voltage or power. Get that wrong and your answer is off by a factor of two. The tool handles it with a dropdown.

How to Use This Signal-to-Noise Ratio Calculator

Pick a preset from the dropdown, or leave it on Custom / manual input.
Choose measurement type: Voltage or Power.
Enter the signal level. It must be greater than zero.
Type the noise level. Also greater than zero.
Watch the hero number update as you type.
Check the four tiles for linear ratio, noise figure, nepers, and signal percentage.
Read the class banner to see how the SNR rates.
Compare against the reference table for common applications.

How the Signal-to-Noise Ratio Formula Works

Signal-to-noise ratio is the ratio of signal power to noise power, expressed in decibels. For voltage, SNR = 20 × log10(signal ÷ noise). For power, SNR = 10 × log10(signal ÷ noise).

Formula: SNR (dB) = 20 × log₁₀(signal ÷ noise) for voltage

Formula: SNR (dB) = 10 × log₁₀(signal ÷ noise) for power

Formula: Linear ratio = signal ÷ noise

Formula: Noise figure (NF) = −SNR (dB)

Formula: Nepers = SNR (dB) ÷ 8.6859

The 20 vs 10 multiplier exists because power is proportional to voltage squared. A voltage ratio of 10 gives a power ratio of 100. In decibels, that’s 20 dB for voltage and 20 dB for power, but the math works out differently. The calculator handles both modes with a dropdown.

Both signal and noise must be greater than zero. Negative values are rejected. Zero is rejected. There’s no upper limit. If you enter a tiny noise value, the SNR can reach hundreds of decibels. If noise exceeds signal, the SNR goes negative, which means the signal is buried.

Worked Example

Switch to Voltage mode. Enter a signal of 2.5 V. Enter a noise of 0.05 V.

Step 1: Find the linear ratio. 2.5 ÷ 0.05 = 50.

Step 2: Take the log base 10. log₁₀(50) = 1.69897.

Step 3: Multiply by 20. 20 × 1.69897 = 33.98 dB.

The calculator reports 33.98 dB. The linear ratio tile shows 50 : 1. The noise figure is −33.98 dB. Nepers: 33.98 ÷ 8.6859 = 3.912 Np. The signal percentage is 2.5 ÷ (2.5 + 0.05) × 100 = 98.04%. The class banner labels this “Good.”

A 34 dB SNR is clean enough for reliable data and clear voice. FM radio sits around 60 dB. CD audio runs near 96 dB. So 34 dB is good, but not exceptional.

Frequently Asked Questions

What is signal-to-noise ratio?

Signal-to-noise ratio is the strength of a signal compared to background noise, expressed in decibels. A higher number means the signal is clearer. A lower number means noise is interfering more.

How do you calculate SNR in dB?

For voltage, use 20 × log10(signal ÷ noise). For power, use 10 × log10(signal ÷ noise). The calculator handles both modes with a dropdown.

What is a good SNR?

For voice, 20 to 30 dB works. For music, 60 dB or higher is good. For WiFi, 25 to 40 dB is reliable. Studio gear often exceeds 90 dB. It depends on the application.

Why does voltage use 20log10 and power use 10log10?

Because power is proportional to voltage squared. Doubling voltage quadruples power. The math gives 20 for voltage ratios and 10 for power ratios to keep decibels consistent.

What is noise figure?

Noise figure is the negative of SNR in dB. It measures how much noise a component adds. Lower is better. A good amplifier might have a noise figure under 1 dB.

What does negative SNR mean?

Negative SNR means noise is stronger than the signal. The signal is buried and may be unrecoverable without heavy error correction. The calculator labels this “Unusable.”

Common mistakes when calculating SNR?

Mixing voltage and power modes, using zero or negative values, and forgetting that decibels are logarithmic. A 3 dB change doubles or halves the linear ratio.

Can I use this calculator for audio?

Yes. Audio SNR is often quoted in dB. A CD player has about 96 dB. A phone call is around 50 dB. Enter your signal and noise levels in voltage mode for typical audio measurements.

What units does this calculator support?

Voltage mode uses volts (V). Power mode uses watts (W). You can enter any positive number. The tool converts nothing else because the ratio is unitless.

What is the SNR of a 16-bit ADC?

A perfect 16-bit ADC has a theoretical SNR of about 98 dB. The calculator includes a preset for that value. Real-world ADCs fall slightly short due to other noise sources.

How do I convert SNR to a linear ratio?

Use the inverse of the formula. For voltage, ratio = 10^(SNR ÷ 20). For power, ratio = 10^(SNR ÷ 10). The calculator shows the linear ratio for you.

What is the difference between SNR and SINAD?

SNR only accounts for random noise. SINAD includes noise and distortion. SINAD is a stricter measure used in audio and radio testing. This calculator does not compute SINAD.