About

In the realm of wireless networking and embedded electronics, power is rarely discussed in whole Watts. Instead, engineers use dBm (decibel-milliwatts), a logarithmic unit referenced to 1 milliwatt. This scale allows for easier representation of the massive losses (attenuation) and gains involved in radio transmission. For instance, a Wi-Fi signal might drop from 0.1 W at the source to 0.000000001 W at the receiver. In dBm, this is simply 20 dBm dropping to -60 dBm.

This tool is designed for network administrators, IoT developers, and ham radio operators. It converts absolute power (W) to dBm with high precision. Correctly understanding this conversion is vital when reading hardware datasheets or configuring router transmission power (Tx Power), as setting levels too high can introduce noise or violate local RF regulations, while setting them too low results in packet loss.

Formulas

The formula adjusts the input Watts to milliwatts before taking the logarithm:

P_(dBm) = 10 × log₁₀1000 × P_(W)

Alternatively, if you know the power in milliwatts (mW):

P_(dBm) = 10 × log₁₀P_(mW)

Key Equivalence: 0 dBm = 1 mW (0.001 W).

Reference Data

Power (W)	Power (dBm)	Common Device / Scenario
1.0 x 10^-13 W	-100 dBm	GPS Signal Received on Earth
1.0 x 10^-9 W	-60 dBm	Good Wi-Fi Signal Strength (4 Bars)
0.001 W	0 dBm	Bluetooth Standard (Class 3)
0.0025 W	4 dBm	Bluetooth Class 2 (10m range)
0.1 W	20 dBm	Standard Wi-Fi Router (2.4 GHz)
0.2 W	23 dBm	Long Range Outdoor AP
0.5 W	27 dBm	Cellular UA (User Equipment) Max
1.0 W	30 dBm	DCS / GSM 1800 Mobile
2.0 W	33 dBm	GSM 900 Mobile Peak
20.0 W	43 dBm	Typical Macro Cell Tower

Frequently Asked Questions

No. 0 dBm represents exactly 1 milliwatt of power. In logarithmic scales, "0" is the reference point (log(1) = 0). Complete silence or no power is represented as negative infinity.

Signal strength drops exponentially over distance. Using dBm allows engineers to simply subtract cable losses and path losses rather than performing complex division with tiny decimal numbers.

dBm is a unit of absolute power (how strong the amplifier is). dBi is a unit of antenna gain (how well the antenna focuses that power). Total radiated power (EIRP) is often calculated as dBm + dBi.

Every increase of 3 dB represents roughly a doubling of power (Watts). Every decrease of 3 dB represents halving the power. For example, 23 dBm is twice the power of 20 dBm.