How to Determine Speaker RMS

by John Smith

RMS is an acronym for “root mean square.” In terms of audio reproduction, RMS indicates the average power output of a loudspeaker. A speaker’s RMS output is measured in watts and is typically listed both on the speaker’s packaging and within the speaker’s documentation. The higher the RMS wattage, the more powerful the speaker. If you aren’t sure of a speaker’s RMS wattage or want to verify a claim made by a manufacturer, you can determine RMS wattage yourself.


Determine the voltage of the speaker. Check the speaker itself, consult the speaker’s specification sheet or use a voltmeter to measure voltage at the speaker.


Determine the amperage of the speaker. Like the voltage, you’ll find the amperage listed on the speaker itself or on the speaker’s specification sheet. You can also use a multimeter to measure amperage at the speaker.


Multiply the speaker’s voltage by its amperage. That figure is the speaker’s RMS wattage.


  • check Don’t confuse RMS output with peak output. A speaker’s peak output represents only a momentary spike in power, but it is often used in marketing materials to give an inflated impression of a speaker’s capability. Scrutinize wattage claims before purchasing speakers.

About the Author

John Smith began his writing career in 2001. He has authored articles on a broad range of topics, focusing most recently on technology pieces for several online publications. Smith holds a Bachelor of Arts and a Master of Arts in international studies.

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