dBm to Watts Calculator
Enter a power level in dBm and instantly get the equivalent in milliwatts and watts — the linear units used in circuit design, link budgets, and equipment specs.
Logarithmic to linear
dBm compresses a million-to-one power range into a tidy scale. This calculator reverses that compression and gives you the true linear power your equipment sees.
Negative dBm is fine
Wi-Fi and cellular signals are almost always negative dBm — that just means less than 1 mW. Enter the negative value as-is; the calculator handles it correctly.
What is dBm?
Decibels relative to one milliwatt
dBm is a logarithmic unit of power measured relative to one milliwatt. It is ubiquitous in RF engineering, Wi-Fi, cellular networks, and fibre optics because it turns the enormous range of real-world power levels — from picowatts to kilowatts — into a manageable scale where every 10 dBm step represents a factor-of-ten change in power. Zero dBm equals exactly 1 mW; 30 dBm equals 1 W.
Enter your dBm value — positive or negative — to get milliwatts and watts side by side.
The conversion raises 10 to the power of dBm divided by 10, which gives milliwatts. Dividing by 1 000 then gives watts.
P(mW) = 10^(dBm ÷ 10) P(W) = P(mW) ÷ 1 000At 0 dBm, 10^(0/10) = 10^0 = 1 mW exactly — the reference point built into the unit's definition. At 20 dBm, 10^(20/10) = 10^2 = 100 mW. At −10 dBm, 10^(−1) = 0.1 mW, a typical received signal level at the edge of a Wi-Fi cell.
The dBm scale makes intuitive sense once you know a handful of reference points. In Wi-Fi and cellular, received signal strength is always negative because a received signal is far weaker than 1 mW. According to industry guidelines, −30 dBm is an excellent signal (you are very close to the access point), −67 dBm is the minimum comfortable level for HD video streaming, −70 dBm supports reliable data, −80 dBm is marginal, and −90 dBm is the noise floor where the connection usually drops.
On the transmit side, a typical smartphone transmits at up to 23 dBm (200 mW) on LTE, a consumer Wi-Fi router at 20 dBm (100 mW), and a licensed amateur radio base station might reach 43 dBm (20 W). Every +10 dBm step multiplies power by ten; a +3 dBm increase roughly doubles it, and a −3 dBm decrease roughly halves it. Knowing this rule of thumb lets you quickly sanity-check any link budget or path-loss calculation.
This calculator performs the mathematical conversion only.
Conversion is mathematical — real-world links are more complex
The formula converts dBm to watts exactly, but actual RF system performance depends on antenna gain, cable loss, path loss, receiver sensitivity, and regulatory power limits. Always consult the relevant standard or a qualified RF engineer before making transmitter power decisions for licensed equipment.