dBm (Decibel-Milliwatt)
The decibel-milliwatt (dBm) is a logarithmic unit used to express absolute power levels referenced to 1 milliwatt (mW). Unlike the relative unit dB, dBm provides an absolute measurement commonly used in radio frequency (RF) engineering, telecommunications, and optical systems.
dBm to Milliwatt Conversion
The power in dBm is calculated from milliwatts as follows:
P(dBm) = 10 × log₁₀(P(mW) / 1 mW)
To convert back to milliwatts:
P(mW) = 10^(P(dBm) / 10)
This allows for intuitive interpretation of power levels across a wide dynamic range.
Key Reference Values
| Power Level | Equivalent in mW |
|---|---|
| 0 dBm | 1 mW |
| +10 dBm | 10 mW |
| +20 dBm | 100 mW |
| +30 dBm | 1 W |
| –10 dBm | 0.1 mW |
| –20 dBm | 0.01 mW |
These values are frequently used in system design and power budgeting.
| Power Level | Details |
|---|---|
| Power Conversions | |
| 0 dBm | Equivalent: 1 mW |
| +10 dBm | Equivalent: 10 mW |
| +20 dBm | Equivalent: 100 mW |
| +30 dBm | Equivalent: 1 W |
| –10 dBm | Equivalent: 0.1 mW |
| –20 dBm | Equivalent: 0.01 mW |
These values are frequently used in system design and power budgeting.
Practical Example
A mobile phone adjusts its transmit power between –30 dBm (1 µW) and +30 dBm (1 W), depending on base station proximity.
A Wi-Fi router typically operates at +20 dBm (100 mW), balancing signal range and energy efficiency.
Such dynamic scaling allows wireless systems to optimize link quality and battery life.
Why Use dBm?
dBm is widely adopted for its practical advantages:
Telecommunications: Measurement of signal strength in cellular, satellite, and wireless networks
RF Engineering: Specification of transmitter power, receiver sensitivity, and antenna gain
Optical Networks: Assessment of laser output and fiber loss
Test & Measurement: Accurate power level tracking in electronic designs
Because it is referenced to a fixed power level, dBm simplifies performance comparison across components and systems.
Related Pages
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