dBm expresses power in decibels relative to 1 milliwatt. It is an absolute power unit, while dB expresses a ratio or change.
How it works in practice
Use dBm = 10 log10(P in milliwatts). To convert back, P in milliwatts = 10 raised to the power dBm/10. Keep the reference unit explicit. Negative dBm means less than 1 mW, not negative physical power.
Example and interpretation
0 dBm is 1 mW, 10 dBm is 10 mW and 30 dBm is 1 W.
Checks before use
- Identify the power unit
- Convert watts to milliwatts
- Apply the logarithm
- Check a known reference value
Important limit
Do not use dB and dBm interchangeably.
Related Centron RF product
SMA 2 W 6 GHz fixed attenuator. Use calculated levels to define a requirement, then compare it with the exact product’s current bandwidth, input power, impedance and available attenuation options. Calculations assume stated conditions and do not replace a component datasheet.
Further reading
Keysight: Fundamentals of RF and Microwave Power Measurements. This background reference explains general principles; the selected Centron RF model’s datasheet governs its own ratings.
Related guides
Educational guide. Numerical examples use the stated assumptions and are not test results for a supplied unit.