# Decibel Watts

**Q:** What is a dBW?

**A:** The decibel is a way of expressing the relative power of something compared to a standard, usually electrical power, current or voltage, or sound levels. In this case it is electrical power relative to one Watt. The decibel is a logarithmic unit, so 10dBW is ten Watts, 20dBW is a hundred Watts and 30dBW is a thousand Watts.

In the European union, the power output of radio transmitters are expressed in dBW's by the licensing authority. In the U.K. this has replaced the old system of quoting transmitter power in Watts. Aerial gain is expressed in dB's, so assuming no feeder loss a 10dBW transmitter connected to an aerial with a 9dB gain would radiate an effective power of 10+9 = 19dBW (80 Watts).

## Decibel Watt Online Calculator

Enter either a value of Decibels relative to one Watt or the actual Watts. Press the Compute button for the calculation other value.

## Practical Application

Receiver sensitivity is usually expressed in dB's relative to a milliwatt or microwatt. The loss of energy as the radio signal propagates from transmit aerial to receive aerial is expressed in dB's. The use of dB's throughout the system makes it easy to calculate through a series of additions and subtraction if a certain signal could be received or not. To convert from dB relative to a Watt to dB relative to a milliwatt add 30. (e.g. 5dBW = 35dBm)

Calculator for dB milliwatt and voltages