dBf to dBm Conversion Calculator

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This tool converts from dBf (deciBel Femtowatt) to dBm (deciBel milliwatt) and Watt.

🔁 dBm to dBf

Formula

dBm = dBf – 120

PdBf = 10*log10(PfW)

1 Femtowatt = 10-15 Watt

1 Femtowatt = 10-12 milliWatt

1 milliWatt = 1012 Femtowatt

Background

dBf is used to specify the sensitivity of Frequency Modulation (FM) Radio receivers. dBm is generally used for RF power measurements.

The term femtowatt (fW) is a unit of power equivalent to 10−15 watts. By expressing signal strength in decibels (dB) relative to 1 femtowatt, dBf allows for a logarithmic comparison of signal power levels. The logarithmic scale is especially useful in RF applications because the range of power levels encountered in these systems is vast.

For example:

  • A signal power of 1 femtowatt equals 0 dBf.
  • A signal power of 1 picowatt (1,000 femtowatts) equals 30 dBf.

The formula to calculate dBf is:

Signal Power (dBf) = 10⋅LOG10​(1 fW / Power in watts​)

Applications of dBf

  • Radio Receiver Sensitivity:
    • dBf is often used to specify the minimum signal strength a radio receiver can detect and demodulate effectively. This value helps compare the sensitivity of different receivers.
  • Broadcasting:
    • In FM and AM broadcasting, dBf is used to quantify the strength of signals received at a specific location, aiding in coverage analysis and quality assurance.
  • Telecommunications:
    • Mobile and satellite communication systems rely on dBf to evaluate the signal quality at the receiver’s end, ensuring reliable communication.