Noise Figure Calculator
Calculate noise figure from signal-to-noise ratios
Linear ratio (not dB)
Linear ratio (not dB)
How to Use This Calculator
Enter Input SNR
Enter the input signal-to-noise ratio as a linear ratio (not in dB). For example, if SNR is 20 dB, convert to linear: 10^(20/10) = 100.
Enter Output SNR
Enter the output signal-to-noise ratio as a linear ratio. This is the SNR after the device adds noise.
Get Noise Figure
Click calculate to see noise figure as a ratio and in decibels. Lower noise figure is better.
Formula
NF = SNRin / SNRout
NFdB = 10 × log₁₀(NF)
Where:
- NF = Noise Figure (linear ratio)
- NFdB = Noise Figure in decibels
- SNRin = Input signal-to-noise ratio
- SNRout = Output signal-to-noise ratio
Example:
SNRin = 100, SNRout = 50
NF = 100 / 50 = 2
NFdB = 10 × log₁₀(2) = 3.01 dB
About Noise Figure Calculator
The Noise Figure Calculator calculates the noise figure of a device or system from input and output signal-to-noise ratios. Noise figure measures how much a device degrades the signal-to-noise ratio. It's a critical parameter in RF amplifier design, receiver systems, and communication links where signal quality is important.
When to Use This Calculator
- RF Amplifier Design: Evaluate amplifier noise performance
- Receiver Design: Calculate overall receiver noise figure
- System Analysis: Analyze noise in communication systems
- Educational Purposes: Learn about noise figure and SNR
Why Use Our Calculator?
- ✅ Accurate Calculations: Uses correct noise figure formula
- ✅ Dual Output: Shows both linear and dB values
- ✅ Easy to Use: Simple interface
- ✅ Free Tool: No registration required
Common Applications
RF Amplifiers: Low noise amplifiers (LNAs) are characterized by their noise figure. A typical LNA might have a noise figure of 0.5-2 dB, while a regular amplifier might have 5-10 dB.
Receiver Systems: Overall receiver noise figure determines sensitivity. Lower noise figure allows detection of weaker signals.
Tips for Accurate Results
- Enter SNR values as linear ratios (not dB)
- To convert from dB: SNR_linear = 10^(SNR_dB / 10)
- Noise figure is always ≥ 1 (or ≥ 0 dB)
- Ideal device has NF = 1 (0 dB) - no noise added
- Lower noise figure is better
Frequently Asked Questions
What is noise figure?
Noise figure is the measure of how much a device degrades the signal-to-noise ratio. It's the ratio of input SNR to output SNR. Lower values are better - an ideal device has NF = 1 (0 dB), meaning it adds no noise.
Why is noise figure important?
In RF systems, noise figure determines system sensitivity. Lower noise figure allows detection of weaker signals. In communication systems, it affects the maximum range and data rate.
What's a good noise figure?
For low-noise amplifiers, noise figures of 0.5-2 dB are excellent. For general amplifiers, 3-5 dB is acceptable. Higher noise figures (10+ dB) indicate significant noise addition.
Can noise figure be less than 1?
No, noise figure cannot be less than 1 (or 0 dB) for a passive or active device. NF = 1 represents an ideal noiseless device. Real devices always add some noise, giving NF > 1.