What is dBm and what are the major conversions used in Optical Network?

MapYourTech March 26, 2025 No Comments Free Technical

Last Updated: August 16, 2025

4 min read

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

dBm:- A mathematical Interpretation.

dBm definition

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 mW to dBm

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 dBm to mW

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 Watt to dBm

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 dBm to Watt

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:

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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