dBm:- A mathematical Interpretation.

MapYourTech March 26, 2025 No Comments Free Standards Technical

Last Updated: August 16, 2025

4 min read

dBm or decibel-milliwatt is an electrical power unit in decibels (dB), referenced to 1 milliwatt (mW).

The power in decibel-milliwatts (P_(dBm)) is equal to 10 times base 10 logarithm of the power in milliwatts (P_(mW)):

P_(dBm) = 10 · log₁₀( P_(mW) / 1mW)

The power in milliwatts (P_(mW)) is equal to 1mW times 10 raised by the power in decibel-milliwatts (P_(dBm)) divided by 10:

P_(mW) = 1mW · 10^(P(dBm) ^{/ 10)}

1 milliwatt is equal to 0 dBm:

1mW = 0dBm

1 watt is equal to 30dBm:

1W = 1000mW = 30dBm

How to convert power in milliwatts (mW) to dBm.

The power in dBm is equal to the base 10 logarithm of the power in milliwatts (mW):

P_(dBm) = 10 · log₁₀( P_(mW) / 1mW)

For example: what is the power in dBm for power consumption of 100mW?

Solution:

P_(dBm) = 10 · log₁₀( 100mW / 1mW) = 20dBm

How to convert power in dBm to milliwatts (mW).

The power in milliwatts (P_(mW)) is equal to 10 raised by the power in dBm (P_(dBm)) divided by 10?

P_(mW) = 1mW · 10^(P(dBm) ^{/ 10)}

For example: what is the power in milliwatts for power consumption of 20dBm?

Solution:

P_(mW) = 1mW · 10^(20dBm ^{/ 10)} = 100mW

How to convert power in watts (W) to dBm.

The power in dBm is equal to the base 10 logarithm of the power in watts (W) plus 30dB:

P_(dBm) = 10 · log₁₀( P_(W) / 1W) + 30

For example: what is the power in dBm for power consumption of 100W?

Solution:

P_(dBm) = 10 · log₁₀( 100W / 1W) + 30 = 50dBm

How to convert power in dBm to watts (W).

The power in watts (P_(W)) is equal to 10 raised by the power in dBm (P_(dBm)) minus 30dB divided by 10:

P_(W) = 1W · 10^( (P(dBm) ^{– 30) / 10)}

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Power (dBm)	Power (dBW)	Power (watt)	Power (mW)
-100 dBm	-130 dBW	0.1 pW	0.0000000001 mW
-90 dBm	-120 dBW	1 pW	0.000000001 mW
-80 dBm	-110 dBW	10 pW	0.00000001 mW
-70 dBm	-100 dBW	100 pW	0.0000001 mW
-60 dBm	-90 dBW	1 nW	0.000001 mW
-50 dBm	-80 dBW	10 nW	0.00001 mW
-40 dBm	-70 dBW	100 nW	0.0001 mW
-30 dBm	-60 dBW	1 μW	0.001 mW
-20 dBm	-50 dBW	10 μW	0.01 mW
-10 dBm	-40 dBW	100 μW	0.1 mW
-1 dBm	-31 dBW	794 μW	0.794 mW
0 dBm	-30 dBW	1.000 mW	1.000 mW
1 dBm	-29 dBW	1.259 mW	1.259 mW
10 dBm	-20 dBW	10 mW	10 mW
20 dBm	-10 dBW	100 mW	100 mW
30 dBm	0 dBW	1 W	1000 mW
40 dBm	10 dBW	10 W	10000 mW
50 dBm	20 dBW	100 W	100000 mW
60 dBm	30 dBW	1 kW	1000000 mW
70 dBm	40 dBW	10 kW	10000000 mW
80 dBm	50 dBW	100 kW	100000000 mW
90 dBm	60 dBW	1 MW	1000000000 mW
100 dBm	70 dBW	10 MW	10000000000 mW