Glossary  >  Decibel-Milliwatts (dBm)

Decibel-Milliwatts (dBm)


To understand decibel-milliwatt, first, we need to understand its constituent parts:

Decibel (dB) is a unit used to express intensity or strength of a signal such as sound or electrical power. On the other hand, a milliwatt refers to a unit of power equal to one-thousandth of a watt.

Decibel-milliwatt (dBm) combines these two units to express the power of a signal through a logarithmic scale with reference to one milliwatt. dBm is a far more convenient way of describing signal power than a milliwatt.

Because it's a logarithmic scale, a small change in a decibel-milliwatt value represents a large change in signal power. This makes dBm more practical in measuring the relatively small changes in signal strength that occur in cell phone signals.

For example, a signal rated at 0 dBm has 1 milliwatt of power, while one rated at -80 dBm has 0.00001 milliwatts, which is significantly weaker.

In cell phone signal boosters, dBm is used to measure the strength of a signal before and after amplification. Typically, a signal strength of -70 dBm or better is considered good, while a signal strength of -110 dBm or worse is considered poor.

Note: The dBm is not part of the International System of Units (SI units). As such, it's discouraged from use in systems that adhere to SI units.

Example of Decibel-Milliwatts (dBm) in a sentence

"Decibel-Milliwatts is the preferred unit for measuring power thanks to its ability to represent low levels of current."

Related Terms for Decibel-Milliwatts (dBm)