Receiver Noise Floor Calculator
Theoretical noise floor (dBm, dBµV) from RBW and receiver noise figure.
Worked example
Input: Resolution bandwidth RBW 120000 Hz, Receiver noise figure NF 10 dB
Result: Noise floor -113.208 dBm, Noise floor (50 Ω) -6.20819 dBµV
Result: Noise floor -113.208 dBm, Noise floor (50 Ω) -6.20819 dBµV
Formula
N = −174 dBm/Hz + 10·log₁₀(RBW) + NF
−174 dBm/Hz = thermal noise at 290 K
How it works
Thermal noise at 290 K is −174 dBm/Hz. Adding the measurement bandwidth 10·log₁₀(RBW) and the receiver noise figure gives a baseline for the smallest level the receiver can resolve. Reducing RBW tenfold lowers the floor by 10 dB.
Practical tipTo trust readings near the limit, the noise floor should sit at least 6 dB, preferably 10 dB or more, below it. Use a preamp if needed, but remember the bandwidth prescribed by the standard cannot be changed freely.
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Results and summaries are for reference. For certification and test reports use the latest official standard text and calibrated instrument data. Last updated: 2026-10-10