dBm to dB Conversion Calculator

dBm (Decibel-milliwatts) is a unit of power relative to 1 milliwatt. dB (Decibels) is a unit of ratio that expresses the relationship between two values of power, voltage, or intensity. It’s also logarithmic.

To convert a dBm value to dB, you need to specify a reference value.

In the calculator, enter dBm value dbm1 and reference value dBm2. The tool will calculate the ratio in dB

🔁 dB to dBm

Formula

dB = dBm1 – dBm2

Example

If

  • dBm1 = 40 dBm
  • dBm2 = 30 dBm

then,

dBm1 – dBm2 = 10 dB

Note that this is not the difference in power level between the two. For that use this calculator.

Instead it is the ratio of powers which has no units.

  • dBm1 = 40 dBm = 10 Watt
  • dBm2 = 30 dBm = 1 Watt

The ratio between the two is 10 and on the log scale it works out to:

10*Log10(10) = 10 dB

Other Conversions

This calculator lets you convert between Volt and dBm.

dB is a relative number and represents a ratio between two quantities. In communications engineering, dB is used to represent the signal-to-noise ratio, gain of an amplifier and more.

Try our other calculators


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