Decibel-milliwatts (dBm) to Watts (W) Conversion
Decibel-milliwatts
The decibel-milliwatt (dBm) is a unit of power expressed on a logarithmic scale relative to one milliwatt (1 mW). It is defined as dBm = 10 × log₁₀(P / 1 mW), where P is power in milliwatts. Used universally in RF engineering, telecommunications, and audio systems: Wi-Fi signal strength is expressed in dBm (typical values −30 to −90 dBm); a 0 dBm signal equals 1 mW; 30 dBm equals 1 W; −10 dBm equals 0.1 mW. Note: dBm cannot be converted with a simple multiplier — it requires the logarithmic formula.
Watts
The watt (W) is the SI derived unit of power, defined as one joule per second (J/s = kg·m²·s⁻³), representing the rate of energy transfer or conversion. Named after Scottish engineer James Watt, whose steam engine improvements launched the Industrial Revolution, the watt is the coherent unit for all forms of power — mechanical, electrical, thermal, and acoustic. A human at rest produces about 80 W of thermal power; a professional cyclist sustains approximately 400 W during a race; a lightning bolt peaks at around 10¹² W for microseconds.
| Decibel-milliwatts (dBm) | Watts (W) |
|---|---|
| 0.1 dBm | 0.00102 W |
| 1 dBm | 0.00126 W |
| 2 dBm | 0.00158 W |
| 3 dBm | 0.002 W |
| 5 dBm | 0.00316 W |
| 10 dBm | 0.01 W |
| 20 dBm | 0.10 W |
| 30 dBm | 1.00 W |
| 50 dBm | 100.00 W |
| 100 dBm | 10,000,000.00 W |
Frequently Asked Questions (FAQ)
What is the formula to convert dBm to watts?
The exact formula is W = 10^(dBm ÷ 10) ÷ 1000. For example: 0 dBm = 10^0 ÷ 1000 = 0.001 W (1 mW), 30 dBm = 10^3 ÷ 1000 = 1 W, and 50 dBm = 100 W. dBm is a logarithmic unit — each increase of 10 dBm multiplies power by 10.
What is 20 dBm in watts?
20 dBm equals 0.1 W (100 mW). Using the formula: 10^(20 ÷ 10) ÷ 1000 = 10^2 ÷ 1000 = 100 ÷ 1000 = 0.1 W. Common reference: typical Wi-Fi transmit power is around 20 dBm.