dB / dBm Converter
dBm is an absolute power unit referenced to 1 mW — used for RF power levels. dB is a dimensionless ratio — used for gain, loss, and power ratios. Two variants exist because power ∝ voltage²:
| dBm | 10·log₁₀(P / 1 mW). 0 dBm = 1 mW, +30 dBm = 1 W, −30 dBm = 1 µW. |
| dB (power) | 10·log₁₀(P₂/P₁). A 3 dB gain = ×2 power, 10 dB = ×10 power. |
| dB (amplitude) | 20·log₁₀(V₂/V₁). A 6 dB gain = ×2 voltage. Use for S-parameters, field ratios, volume. |
Type in either field — the other updates automatically.
Power
Decibels
\begin{align} P_{dBm} &= 10\log_{10}\!\left(\frac{P_W}{1\,\text{mW}}\right) \end{align}
For power ratios — use this for insertion loss, antenna gain, noise figure, cascaded gain.
Linear power ratio: —
dB: —
\begin{align} \text{dB}_{pow} &= 10\log_{10}\!\left(\frac{P_2}{P_1}\right) \quad\Longleftrightarrow\quad \text{ratio} = 10^{dB/10} \end{align}
For voltage, current, field, or any amplitude ratio — use this for S-parameters, audio volume, voltage gain.
Linear amplitude ratio: —
dB: —
\begin{align} \text{dB}_{amp} &= 20\log_{10}\!\left(\frac{V_2}{V_1}\right) \quad\Longleftrightarrow\quad \text{ratio} = 10^{dB/20} \end{align}