RF power unit conversion: enter dBm or mW and get the equivalent in all power and voltage units. Vrms assumes a resistive load at the specified reference impedance Z₀ (default 50 Ω).
dBm ↔ mW ↔ Vrms Converter
Parameter
Value
Power (dBm)
--
Power (mW)
--
Power (W)
--
Vrms into Z₀
--
Vpp (sine)
--
Formula & Theory
dBm to mW: P(mW) = 10dBm/10
mW to dBm: dBm = 10 × log₁₀(P(mW))
Power to Vrms: Vrms = √(P(W) × Z₀)
Sine Vpp from Vrms: Vpp = 2√2 × Vrms
Reference: 0 dBm = 1 mW = 224 mVrms into 50 Ω
Worked Example
Common reference levels:
−10 dBm = 0.1 mW = 70.7 mVrms into 50 Ω (typical signal generator default)
0 dBm = 1 mW = 223.6 mVrms = 632 mVpp into 50 Ω
+10 dBm = 10 mW = 707 mVrms = 2.0 Vpp into 50 Ω
+20 dBm = 100 mW = 2.24 Vrms = 6.32 Vpp into 50 Ω (1/10 W PA output)
+30 dBm = 1 W = 7.07 Vrms into 50 Ω
Assumptions & Limitations
Voltage calculations assume a purely resistive load at Z₀ — reactive loads change the relationship
Vpp formula assumes a single-frequency sine wave — complex waveforms require peak detection
Average power assumed — peak power for pulsed signals is higher
Common Mistakes
Confusing dBm and dB: dBm is an absolute power level; dB is a ratio. A "10 dB attenuator" reduces power by 10 dB (factor of 10), not to 10 dBm.
Wrong impedance reference: TV/cable systems use 75 Ω — converting dBm to voltage in a 75 Ω system using the 50 Ω formula gives the wrong voltage. Set Z₀ correctly.
Peak vs average power: For pulsed or modulated signals, dBm typically refers to average power. Peak power can be 3–10 dB higher depending on modulation type and peak-to-average power ratio (PAPR).
Parts to Consider
Representative part categories — verify specifications match your design requirements before ordering.
Fixed RF Attenuators (SMA, 50 Ω)Precision 50 Ω SMA attenuator pads, 1–30 dB — for signal level adjustment and impedance matching
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dBm is decibels relative to 1 milliwatt. It is an absolute power level, not a ratio. 0 dBm = 1 mW, +10 dBm = 10 mW, +30 dBm = 1 W, -10 dBm = 0.1 mW. The formula is: P(dBm) = 10 × log₁₀(P(mW) / 1 mW).
Why does the voltage conversion require a reference impedance?
Power is P = V²/R, so voltage depends on the impedance of the system. In RF systems, 50 Ω is the standard; in some audio and telecom applications, 75 Ω or 600 Ω are used. Specify Z₀ for your system — the Vrms shown is the voltage across that impedance when delivering the specified power.
What is the power level of a typical WiFi or Bluetooth transmitter?
Most WiFi adapters transmit at +15 to +20 dBm (32–100 mW). Bluetooth Classic transmitters are typically +4 to +20 dBm. BLE devices often transmit at 0 dBm (1 mW) or lower for power efficiency.