dBm to milliwatts

dBm is defined against the milliwatt, so converting dBm back to milliwatts is the most direct conversion in RF: 0 dBm is exactly 1 mW, 10 dBm is 10 mW, and 20 dBm is 100 mW. A Bluetooth radio at 10 dBm transmits 10 mW; a Wi-Fi card at 20 dBm pushes 100 mW. Signal generators and receiver sensitivity specs live entirely in this range.

mW = 10^(dBm ÷ 10). The decibel scale is anchored at one milliwatt, so 0 dBm is exactly 1 mW, 10 dBm is 10 mW and 30 dBm is 1 W. Powers multiply while decibels add.

By EnginStack Editorial Team | Reviewed against NIST, BIPM and primary-source documentation About →
dBm
— milliwatts
— —

Authority: NIST SP 811 (SI usage guide) and the 1959 International Yard and Pound Agreement. The coefficient above is a defined value — it does not come from measurement and carries no uncertainty.

dBm to milliwatts

The formula P(mW) = 10^(dBm/10) is exact — dBm means decibels relative to one milliwatt, so the definition itself is the conversion. The practical range is enormous: receiver sensitivity sits around −90 dBm (a picowatt), while transmitters run +20 to +40 dBm. This calculator handles the transmitter side, where mW is a readable number, and it is the unit most test equipment agrees on.

milliwatts = 10^(dBm / 10)
0 dBm = 1 mW  ·  10 dBm = 10 mW  ·  20 dBm = 100 mW
The conversion is exact by the definition of dBm.

Worked Examples

Example 1: Convert a Wi-Fi card rated at 20 dBm

10^(20/10) = 10² = 100 mW

Example 2: Convert a 10 dBm Bluetooth radio

10^(10/10) = 10¹ = 10 mW

Example 3: Convert a 30 dBm transmitter

10^(30/10) = 10³ = 1,000 mW

Common dBm to milliwatts Values

dBmmilliwattsContext
0 dBm—1 mWThe dBm anchor.
10 dBm—10 mWBluetooth Class 1.
20 dBm—100 mWWi-Fi transmit.
23 dBm—200 mWWi-Fi at max.
30 dBm—1,000 mW1 W — regulatory limit.

Engineering Context

dBm-to-mW is the tightest pairing on the electric hub — the milliwatt is the definitional base of dBm, so mW to dBm and dBm to watts are the same number shifted by three decades. The energy family takes over at watt scale.

dBm is a ratio expressed on a logarithmic scale, referenced to exactly one milliwatt, so converting back to milliwatts is an exponentiation rather than a multiplication. Two consequences follow and they are the reason RF engineers work in decibels at all. First, a change of ten decibels is a factor of ten in power, so a link budget is built by adding and subtracting gains and losses instead of multiplying factors. Second, the sensitivity of a receiver, often specified around minus one hundred dBm, is ten to the minus tenth of a milliwatt, a number that is unusable in its linear form and routine in its decibel form. Rounding matters: a half decibel is twelve percent of the power.

More: mW to dBm · dBm to W · W to dBm · Electric Guide · Electric Hub

Related Unit Converters

milliwatts to dBm dBm to watts watts to dBm Electric Conversion Guide Electric Converters

Frequently Asked Questions

How many milliwatts is 0 dBm?

Exactly 1 milliwatt — that is the definition of dBm. Each 10 dB multiplies the milliwatts by 10: 10 dBm = 10 mW, 20 dBm = 100 mW.

What power does Bluetooth transmit?

Class 1 Bluetooth transmits at 20 dBm (100 mW); Class 2 — the common low-power mode — at 4 dBm (2.5 mW). This converter covers both with the same formula.

How do I convert dBm to mW by hand?

For every 10 dB add a zero: 0 dBm = 1 mW, 10 dBm = 10 mW, 20 dBm = 100 mW. For in-between values use 10^(dBm/10) exactly.