What does RMS (Root Square Mean) Mean?

by Matthew David | Updated: 08/19/2019

What is RMS? You see and hear the term in product descriptions of speakers amidst other technical numbers like peak power, frequency range, dB ,sensitivity and OHMs. While those numbers are all important, RMS in particular is a number you should pay extra attention to.

To help build an ideal sound system for either your car or home, it’s important to have a grasp of these terms so that you can maximize your system’s performance. I would argue that in addition to price, RMS may be the most important number to pay attention to when buying car speakers.

What Does RMS Mean?

RMS stands for Root Square Mean – In short, it represents the average power output of your speaker (or amplifier).

For example, a speaker maybe advertised as having 150W in peak power, but its RMS may only be 50W. It is this lower 50W number that the speaker will produce over prolonged periods, while the peak power of 150W will only occur intermittently.

Though the RMS number may not always be precise, it is the best measurement by which to measure a speaker’s power output.

Why Peak Power instead of RMS?

It comes down to marketing. A brand would like to move as many units as possible. People associate larger numbers with more power. Therefore, it makes sense that manufacturers advertise a speaker’s peak power because this number will be higher than the speaker’s average power – or RMS.

Peak power is nice to know, but when comparing speakers, look at the speakers’ RMS as a tru representation of their power.

RMS Continued

Armed with a better understanding of RMS, you’ll be in a better position to configure your car’s sound system (amp, subwoofer, head unit, speakers etc…)

Reputable brands have their products CEA tested and certified, ensuring that the sound specifications are accurate and truthfully advertised.

While this is certainly comforting, if you really want your sound to be crisp, clear and loud, you should be mindful of the power feeding your car’s sound system.

For example, if you only have car speakers to power in a midsized vehicle, you could probably get away with a 50W head unit. However, if you’re powering speakers in a larger vehicle, or powering a subwoofer, you’ll definitely need an amplifier.

Be sure to line up your amplifier’s power with that of your head unit and speakers. Pro tip, your speakers can actually handle anywhere from 75-150% of the advertised RMS of your amplifier.  Ideally, however, your amplifier’s output should have the same wattage as the RMS of your speakers and subwoofers.

We’ve covered a wide range of car speakers and subwoofers spanning a number of different sizes and price points so be sure to check our buyer’s guides.