Last Updated: August 16, 2025
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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:
P(W) = 1W · 10( (P(dBm) – 30) / 10)
For example: what is the power in watts for power consumption of 40dBm?
Solution:
P(W) = 1W · 10( (40dBm – 30) / 10) = 10W
How to convert dBW to dBm
How to convert power in dBW to dBm.
The power in dBm is equal to the base 10 logarithm of the power in watts (W):
P(dBm) = P(dBW) + 30
For example: what is the power in dBm for power consumption of 20dBW?
Solution:
P(dBm) = 20dBW + 30 = 50dBm
How to convert dBm to dBW
How to convert power in dBm to dBW.
The power in dBW (P(dBW)) is equal to 10 raised by the power in dBm (P(dBm)) divided by 10:
P(dBW) = P(dBm) – 30
For example: what is the power in watts for power consumption of 40dBm?
Solution:
P(dBW) = 40dBm – 30 = 10dBW
dBm to Watt, mW, dBW conversion table
| 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 |
Optical Communications & Network Automation Expert | Author of 3 Books for Optical Engineers | Founder, MapYourTech
Optical networking engineer with nearly two decades of experience across DWDM, OTN, coherent optics, submarine systems, and cloud infrastructure. Founder of MapYourTech. Read full bio →
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