Decibelmilliwatt

Decibel-milliwatt, abbreviated dBm, is a unit of power level used primarily in radio frequency (RF) engineering and telecommunications. It expresses a power value relative to a reference of 1 milliwatt (mW) on a logarithmic scale. The defining equation is P(dBm) = 10 log10(P / 1 mW), where P is the power in milliwatts. Equivalently, P(W) = 0.001 × 10^(dBm/10).

Because dBm measures absolute power, it is convenient for describing transmitter output, received signal strength, and link budgets across RF systems. For example, 0 dBm equals 1 mW, 10 dBm equals 10 mW, and 20 dBm equals 100 mW; negative values indicate powers below 1 mW (e.g., −30 dBm = 1 µW).

dBm is widely used in wireless and networking contexts such as Wi‑Fi, Bluetooth, cellular networks, and RF front ends. It is common to specify transmit power, receiver sensitivity, and signal strength in dBm, often alongside gains, losses, and noise figures to assess link viability.

Notes: dBm is a power ratio expressed with a fixed reference of 1 mW. The actual voltage or field strength corresponding to a given dBm value depends on system impedance; in RF practice, 50 ohms is a common reference, so voltage relates to power by V = sqrt(PR). dBW (decibel-watt) is a related unit referenced to 1 watt.