dBm / mW / W / dBW Converter

The decibel was standardized by Bell Labs in 1924, named in honor of Alexander Graham Bell. Originally a unit for measuring telephone-line attenuation in "transmission units" referenced to 1 mW into 600Ω (standard telephone impedance), "dBm" — decibels relative to 1 mW — became the universal RF power unit within decades.

The 1 mW reference was chosen because it represented typical telephone-network signal levels in the 1920s — low enough to be measurable over long cables, high enough to drive early vacuum-tube amplifiers. It was written into Bell standards and never superseded, even as power levels in modern RF span ±200 dBm from deep-space receivers to megawatt radars.

dBW (dB relative to 1W) is used in satellite and broadcasting engineering where power levels are higher; dBm stays dominant in wireless handset and small-signal engineering. Scientific/academic contexts sometimes use dBmW explicitly to avoid confusion; in practice, "dBm" is universally understood.

Type in any of the four fields; the others update instantly. Covers standard RF power-level conversions. No impedance correction is applied — all four units assume the same reference impedance (typically 50Ω for RF). If you\'re converting between voltage (dBV, dBµV) and power-level units, you need the impedance term; use the decibel calculator instead.

Common references: +0 dBm = 1 mW (GPS received signal, -130 dBm; typical Wi-Fi RX signal -50 to -80 dBm; cellular phone TX peak +23 dBm = 200 mW). Everything runs client-side.