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What is the difference between dB and dBm?

Asked by Deborah , Last updated: Sep 16, 2020

H. Martin

H. Martin, Content Writer, Charlotte

When a physical amount, such as power or intensity, is measured relative to a reference level, it is expressed in decibels, which is dB, a logarithmic unit. Decibel is considered division less because it is a ratio of two quantities with the same group and cancellation occurs. It is utilized for quantifying the ratio between two values. The best example of this is the signal to noise ratio.

The sound pressure level is normally measured in dB, but the unit is not restricted to that quantity only. There are many uses of this measuring unit, usually in engineering. Since it is relevant in measuring signals, anything that can be conveyed in waves may also be calculated with dB. In the disciplines of audibility electronics, dB is copiously utilized. dBm is different, yet similar to dB.

dBm stands for an absolute power level. It is about another unit of power milliwatt. The value of “P” is in watts. You can transform the absolute power unit “P” into dBm. Based on what value the power can be in any kind. dB is used to quantify the ratio between intensity or power values, while dBm is used to express an absolute amount of power.

C. Lopez

Driving down to Knowledge town

C. Lopez, Chauffer, Chauffer, Watertown

There are a lot of people who may become confused with dB and dBm, mainly because they think that these two are the same. When you say dB, this is known to be a dimensionless unit. This is different from a dBm, which is known to be an absolute unit.

There are people who will use dB for the different power values that are available, while the dBm will show the absolute value of power. If you are wondering when these are normally used, you should realize that they are done for fiber optic networks that are being tested. There is a formula that is normally used in order to create dB.

Both db and dbm stand for different things. dB stands for decibels. dBm stands for absolute power level. dB and dBm both have different ways to calculate them. dB is expressed as the following: dB = 10 log (P1/P2). dBm is expressed as dBm = 10 log (P/1mW). A person would use dB to make a numerical ration between power values, as well as two intensity values. dBm is used to express the power's absolute value. dB has no dimensions, while dBm is absolute. Another difference between them is that they are relative to different things. dB is relative to input signals, while dBm is relative to mW signals.