Speaker Ohms Calculator – Series / Parallel / Series-parallel, speaker power, and more!

Welcome! I’ve worked hard to create what I think is the best speaker Ohms calculator on the internet for you.

My speaker Ohms calculator will let you:

  • Find the total speaker Ohms for almost any series, parallel, or series-parallel speaker wiring.
  • Find the total power your amp or stereo will output (or warn you when it can’t produce that amount of power).
  • See the power supplied to each speaker for your wiring configuration.
  • Find out if your speaker setup could cause amp or stereo damage before you try it out.

Note: Javascript must be enabled in your browser to see or use the tool.


speaker Ohms calculator section image


Choose your speaker configuration/wiring:

  1. Series connected speakers
  2. Parallel connected speakers
  3. Series-parallel speakers: up to 4 “strings” of 1-4 series speakers, all series strings in parallel. (*Using 1 speaker in each string will effectively be the same as the Parallel speaker option)
  4. Parallel-series: up to 4 speakers in parallel which are then in series with 1 or more speakers.

Input your speaker Ohms and power values:

  1. Speaker impedance (Ohms): Fill in the speaker Ohms value for as many or as few speakers as you’d like.
  2. OPTIONALAmp/stereo power & min. Ohms rating: Input the amplifier or stereo’s power (RMS or continuous) power rating and the min. specified speaker Ohms. This will allow the calculator to determine power to each speaker in any configuration.

You can use whole numbers (2, 5, etc.) or decimal values (6.3Ω, etc.) for Ohms as needed. If using the power option, use the RMS or continuous power rating in whole Watts for your amplifier or stereo. “Peak” or “maximum” ratings are misleading and will give the wrong results.

The speaker Ohms calculator will output:

  • Total speaker Ohms: This is the total speaker load the amp or radio will see based on the speaker Ohms you’ve entered.
  • [Optional] Total power draw from the amp or stereo: This shows the total amount of power the calculated speaker Ohms load will draw from the amp or stereo.
  • NOTE! If the total speaker load would draw excess current (exceed the power rating you specified), this means an unsafe condition would happen and you’ll see “–” to indicate an error/invalid power amount.
  • [Series-parallel option] String (“Strx“) ohms: The series Ohms value for each string of speakers, 1 to 4 speakers each.
  • Power to each speaker (“Sx“): Power, in Watts, each speaker will receive.

How to calculate series, parallel, or series-parallel speaker Ohms (DIAGRAM and examples)

how to calculate speaker ohms series parallel diagram

Figuring out the total Ohms speaker load for nearly any wiring configuration isn’t as hard as it may seem. As you can see from my diagram above, there are 3 main ways to do this:

  1. Find the total series speaker Ohms.
  2. Find the total parallel speaker Ohms.
  3. Using a combination of #1 & #2 for more complicated speaker systems.

1. How to find the total series speaker Ohms value

These are the simplest to deal with. To find the total speaker resistance (impedance) for series speakers, simply add them all together.

For example, let’s say we have 3 speakers we’d like to use: two 8 ohm and one 16 ohm.

We’d just add these together like so: 8Ω + 8 234 + 16Ω =  32Ω 

When speakers are connected in series, they share the same electrical current. The amplifier, radio, or stereo’s power will be divided among them. Note that if the total speaker load is higher than the maximum power output Ohms rating for your amp or stereo, the total power you can get will be lower.

(I’ll go into more detail about this in another section below)

2. How to calculate the total Ohms load for parallel speakers.

parallel resistance formula diagram

When it come to finding the total speaker impedance for parallel wiring, there are two ways to do this:

  1. If the speaker Ohm ratings are all the same, you can just divide by the number of speakers used.
  2. For parallel speakers of the same or different values, you can use the universal parallel speaker formula below. You can call this the “inverse sum of the reciprocals”, which just means we add up all the inverse (1/x) values then take one final inverse function to get the result. (I’ll explain how to do this.)

Example #1: Let’s say we have three 4 ohms speakers wired in parallel. We can use simple division to find the total speaker load:

Rparallel = 4Ω/3 =  1.33Ω 

Example #2: In this example, we have four speakers of different values: two 8 ohm and two 16 ohm speakers, all wired in parallel. What is the total speaker load?

Rparallel = 1/(1/8 + 1/8 + 1/16 + 1/16)

                   = 1/(.125 + .125 + .0625 + .0625)

                    = 1/(0.375) =  2.67Ω 

3. Series-parallel and other wiring types

For anything other than just series or parallel speaker wiring, we can just break it down into a few of same calculations and then add them all together.

Example #3: We have four “strings” of four 8 ohm speakers each. All four series strings are wired in parallel. We can solve this pretty easily!

(a.) Finding the series speaker Ohms: each string of four speakers is 8Ω + 8Ω + 8Ω + 8Ω or 8Ω x 4. This is 32Ω total for each series string.

(b.) Find the total parallel speaker Ohms: we have four strings, so this is 1/(1/32 + 1/32 + 1/32 1/32) or just 32Ω/4 since they’re all the same value. 

So the total is 32Ω [each series string] / 4 strings =  8Ω total in series-parallel 

How to find parallel speaker ohms (inverse sum of reciprocals) on a calculator

example of the inverse (reciprocal) key on a calculator

Many calculators (especially scientific ones, although that’s not a requirement) have an inverse function.

An inverse key (inverse function, or reciprocal function) is simply dividing one by some number. Having a button handy makes it much faster and less likely you’ll make a mistake, too.

Note: The inverse button is sometimes also be written as a negative power of 1 (“^-1”) as it’s mathematically identical.

Let’s take example #2 from earlier to show how you can easily find any parallel speaker load using a calculator. I’ll show where I’m using the buttons you’d use on a real calculator.

(Example #2: We have four speakers of different values: two 8 ohm and two 16 ohm speakers, all wired in parallel.)

(a.) You would enter on your calculator:

8 1/x 8 1/x 32 1/x 32 1/x

which will give 0.125 + 0.125 + 0.0625 + 0.0625 = 0.375

(b.) Then we’ll take the reciprocal (inverse) of this to get our result:

0.375 1/x = 2.67 Ω (rounded from 2.66666… as we don’t need that much precision).

example of sum of reciprocals in a pretty print scientific calculator

You might find it helpful to use a scientific “pretty print” calculator as they display the math you’re entering just like you’d write it on paper. This helps you be sure of what you’re entering as you go.

Amplifier power vs the speaker Ohms load

diagram showing how power is shared between series or parallel speakers

The total speaker load you end up with can have a very big impact on the power you can use. That’s because home or car stereos, amplifiers, and radios can only produce up to a certain output voltage to deliver power to speakers. If the speaker load (Ohm value) is higher, they can’t deliver as much electrical current, resulting in a lower total power provided.

How to calculate amp and speaker power for different speaker loads

Example #1: How to estimate total amplifier power at different speaker Ohm loads

For example, let’s use an example of a guitar amplifier that can provide 50 watts RMS continuous per channel into a min. of 8 ohms. As power is related to voltage and resistance, we can rearrange the formula for power to help us:

(a.) Power (P) = (Voltage (V))^2 / Resistance (R)

We can rearrange this to find voltage: Voltage (V) = square root(Power x R)

(b.) Doing a little bit of math, that means the output voltage at full power into an 8 ohm speaker would be:

V = square root(50 x 8) = √(400) = 20V(Max. output)

What happens if we connect two 8Ω woofers in series? How much power can we expect?

This would be (20V)^2 / 16Ω = 400/16 =  25 Watts 

This makes sense! After all, the electrical current decreases as the resistance increasesTherefore, the amp can’t deliver as much power at 16Ω as it can at its 8Ω specification. There’s nothing wrong with using a higher impedance speaker load, but you’ll have to live with the compromise and less overall power.

Example #2: Estimating power to each speaker vs the total power delivered

Using example #1 above, we have 25W delivered in total to our 16Ω speaker load. For speakers in series, you can find the power each speaker will get even if they have different Ohm ratings.

In this case, we can use: Pspeaker = Ptotal (total power) x Speaker1/(Speaker1 + Speaker2)

This gives us: P1 (power to speaker one) = 25W*8/(16) = 25W*0.5 =  12.5W 

So each speaker will receive 12.5W in this case which is 1/4 of what a single 8 ohm speaker would receive for this amplifier.

What speaker Ohm load should I use for the best power?

what speaker ohms load is best for power section image

When using multiple speakers the best Ohms load for power is the lowest acceptable total speaker load the stereo or amplifier is rated to handle at maximum power output.

This is because many amplifiers (and some radios and stereos etc.) have their maximum power output possible at the minimum Ohms rating specification. This is sometimes called the Ohm rating they are “stable to.”

For example, a 2Ω stable car subwoofer amplifier may be rated like this:

  • 250W x 1 @ 4 ohms
  • 500 W x 1 @ 2 ohms

The specifications tell us:

  • This amplifier is designed to handle as low as 2 ohms minimum
  • It will produce maximum power output (maximum current) safely at a total speaker load of 2 ohms

This means to get all the power we paid for, we’ll ideally have a total speaker load that adds up to 2Ω. The problem is that when using multiple speakers it can be difficult to get match the min. speaker Ohm rating.

You’ll have to match at least the min. acceptable Ohms rating specified. Too low of a rating (say 1Ω in this case) and the amplifier can shut off, overheat, or suffer permanent damage.

Using dual voice coil speakers may help as they offer multiple speaker ohms configurations. However, it’s very common (especially if you’ve already bought speakers) to not be able to get the “perfect” total speaker Ohms load. 

You’ll have to live with some compromises which may mean less total power available.

About the author

Marty is an experienced electrical, electronics, and embedded firmware design engineer passionate about audio and DIY. He worked professionally as an MECP-certified mobile installer for years before moving into the engineering field. Read more »

Your comments are welcome.
  1. Not sure that I missed it or if it is here but I am trying to calculate the outcome of using two different size tweeters. One is a 4 ohm and the other is an eight ohm. Think the total own load in parallel is going to be something like 2.6666. wattage of the amp at 4 ohms is 198 watts and at 2 ohms it is 300 Watts. Would one speaker get more wattage than the other or would it be divided evenly and would one play louder than the other if they have similar wattage requirements? Thank you for your help

    • Hi Geoffery. To answer your questions:

      1. Yes, if the speakers have different impedances, they’ll get different power levels. That’s because for the same output level from an amp the voltage across an 8Ω speaker isn’t enough to develop the same power. It will develop 1/2 the power of the 4Ω speaker.

      That’s one reason home stereo receivers & amps have a higher output voltage – they have to in order to deliver more power to a higher impedance (8Ω) speaker.

      2. It depends on their sensitivity (dB per Watt/Meter specification), but basically once you start increasing the amp’s volume/output, the 8Ω speaker’s power & volume will fall behind that of the 4Ω by several decibels. realistically speaking it won’t “hurt” anything, but yeah they won’t have the same power & volume levels.

      I hope that helps! Best regards.

  2. How to wire 2 individual powered subwoofer to my stock radio? Do I have to run 2 individual power wires.? Can one sub connect to the front speakers and the other the rear?

  3. Hi Marty
    Great site and I appreciate you passing along your knowledge. Honestly knowledge is the foundation to everything Imho. I am looking at putting in 2 RF 1694 6×9 4way 4ohm speakers in front doors of 2019 4runner. I’m getting mixed answers about fitment. I’ll give measurements from Crutchfield on specifics in regards to my vehicle at bottom. Now I’ve heard with a metra bracket I’m good. From Crutchfield!!! Close but good. No window block. I’m worried with bracket my grill will be in way or possibly panel not go back on proper. I’m running a 400w 4ch with back doors in near future. I can switch to 2ch til then. Ive been keeping up with your page and think you will be the answer, good or bad, that I’d most trust. Here are measurements Size:6×9″
    Mounting height:0.795
    Major apex diameter:8.555
    Minor apex diameter:5.565
    Screw hole alignment:
    Not possible
    Now I know I can self tap in if it drops in without blockage but before I take apart Id like to hear from you who has no skin in the game.
    Hope to hear your response so drop some knowledge on me!

    • Hello there. To be honest, I never rely strictly on speaker size guides. One reason is because a speaker may technically fit but not line up properly, may have big air gaps around it, or might not fit correctly at all despite supposedly being recommended as correct.

      The best thing to do is pull the door panel off and check it yourself – that way you can find out for 100% sure. It’s not unusual to need an adapter or sealant around the speaker (silicon works well, self-adhesive foam, etc.). I personally use a cordless drill with Phillips head screw bit & 3/8″ or 1/2″ #8 self-tapping screws to make it fairly easy and quick.

      While factory speakers are often *close* to a standard aftermarket speaker size, typically they’re slightly off and require a little bit extra to get an aftermarket replacement to fit well. In your case however it shouldn’t be very difficult.

      I would definitely (if possible) remove the door panel and check fitment with the glass rolled down. I hope that helps!

      • You the man Marty! Thanks for quick response and can’t believe I didn’t mention sound quality! Better safe then sorry. I agree with there’s always wiggle room, good or bad, with supposed standards and you do present safest route. I wish I was close enough to have your business do it because in the past I’ve done my share of installation (in old man voice)..like Ken 1020 amps and early Fosgate Punch amps Boston Acoustics tweets JLA mids and subs w/ridiculous sized mags w/ Alpine pullouts and then removable faceplates. What a huge deal it was to be able to slide your stereo out and be able to turn your stereo display from Alpine blue to Amber. Anyway I digress cause while removal is a lot easier you need your type of degrees to do a proper install that sounds like a concert in your mobile man’s den. Meaning proper Spatial sound correct air space, ohmage vs wattage and voltage etc. I consider myself a amateur audiophile and hear the difference from proper install from self install. And not some cookie counter franchise where all you need is to be able to splice wires you’re hired. I’m rambling but I do think it’s cool that I have the RF amp you recommend and already have the Fosgate Punch enclosed Sub which is a no brainer hookup. I have a JLA vs RF crisis when buying but I do disagree when it comes to MTX….I would’ve gone JL Audio JD400/4 just my opinion. Anyway thanks for responding and great page and like the “You can do it” advice. Sorry I’m writing a small novel here.lol. Hope this rambling won’t let me pick your brain every now and again.
        P.S. Roll Tide Sucks!!!!

        • Hey TK I get where you’re coming from. Yeah, unfortunately sound quality has really been I dare say a “lost art” for some time in car audio. But fortunately we have a lot more (and more affordable!) options these days.

          So if you get a pretty decent setup you can get great sound quality and even stereo imaging without spending a ton. I personally did use a digital signal processor with time delay to help fix my stereo image (left channel is often a mess). Have a great day and War Eagle, ha ha!

  4. Hello Marty,I have found you site to be so helpful to me especially when trying to understand how to connect speakers
    I have 3 6ohms speakers with a minimum 6ohms system,what’s the best way I need to connect them for great balanced sound?
    Looking forward to a response please,thank you

  5. Hello Marty,I have found your site to be so helpful to me especially when trying to understand how to connect speakers
    I have 3 6ohms speakers with a minimum 6ohms system,what’s the best way I need to connect them for great balanced sound?
    Looking forward to a response please,thank you

  6. I would like to upgrade my present speakers in my 7-speaker Bose system in my 2021 GMC Canyon. The problem I have is that the Bose systems have specific ohms value that are difficult to match. The present ohm values are 3.2 ohms L&R front, 3.35 ohms Center dash, 1.7 ohms front doors, and 3.2 rear doors. Replacements would be 4 ohms L&R front, 4 ohms Center dash, 2 ohms front doors, and 4 ohms rear doors. I am dealing w/crutchfield and this is the closest in ohm values they have to replace my bose speakers. I understand that an increase in resistance would effect power output by the amp. In this example of impedance value differance would it be ok. Would the power output differance be minimal or would it be such that it would not be worth to go ahead with the changes. The Bose amplifier has 7 channels of custom equalizatioan and proprietry signal processing.

    • Hi, yes as long as you use the same or higher impedance speakers, it should be fine. In this case, it’ll be very minimal power loss, including the front speakers. The aftermarket 4Ω & 2Ω speakers are in reality pretty close to the Bose speaker impedances so I wouldn’t worry.

      Best regards.

      • Hi Marty,

        Thank you for your response to my situtation. You mentioned very minimal power loss. Is it possible to define very minimal power loss to a % of volume I might lose?
        Also, is this analogy accurate? Replacing a 4 ohm speaker with a 3.2 ohm speaker.
        3.2/4 = 80% so therefore a 20% power loss in the speaker?

        • Well, there are ways to find a more accurate estimate of the power difference. We’d need to know the DC resistance & inductance in the voice coil of the aftermarket speakers. Unfortunately, that’s rarely supplied with car speakers. I’m going to assume the 3.2Ω Bose speaker rating is the DC resistance as well? As I’m not clear on that.

          As a 4Ω speaker has a DC resistance of say somewhere around 3.6 Ohms, let’s use that. That gives a difference of somewhere around 12% difference in power (a rough estimate). I think that’s fairly realistic all things considered.

          However, 12 or even 20% difference in power isn’t equal to that in volume loss. Volume changes by 3 decibels for every doubling of the power so you shouldn’t notice much difference in volume in this case.

          • Thanks again for your help. I will go ahead with the project and get back to you with the results.
            Thanks again.

  7. Marty,
    If I have 3 buttkicker lfe mini (transducers) 4 ohms each rated min 50 watts max 250 , is it best to get a 2 channel amp and wire 2 parallel or mono and wire in series? What size amp would you recommend as well? Would it be beneficial to have 4 transducers to wire in series/parallel to keep it even?

    • Hi, if the 2 channel amp is 2 ohm stable (many are these days), you could get by with it having two on one channel in parallel and one on the 2nd channel. The two on one channel however would split the available power.

      You’d be better off using a 4 channel amp, though, if you want even power to each transducer. There’s really not a great way to use 3 on a 2 channel amp, at least not with even power distribution.

  8. Hi Marty, I have a NuTone intercom system and the outdoor speaker in the pool area doesn’t work. The burned out speaker is a 25ohm 5″. Do you think I could install 2 or 3 8ohm speakers off the channel or intercom station? I would guess there are 7 or 8 remote stations each with it’s own channel in the intercom system. There are 2 16v 30 watt transformers in the Master panel. I don’t know if that means The system is 60 watts or 30 watts with 2 channels but runs 8 stations? The outdoor speaker is in a face plate but i was thinking I would buy a remote control unit that has only the control buttons and no speaker then use 2 or three 8 ohm speakers in series. Do you think 2 rather than 3 speakers would be the right direction, because of the lack of wattage, or is matching the ohms more important. The other option is buying 25 ohm speakers but I’m thinking there is not much wattage pushing the single (I’m assuming) channel. My other thought was the 5″ speakers sound tinny (Like an ancient transistor radio) and I would get 8″ 8ohm speakers and hopefully get better sound? Can you lend any insight to intercom speaker problems. The problem has been isolated to the speaker and it looks to me like it was an indoor speaker used outside. Also do all speakers work as a microphone back into the intercom? If not should I look for an 8 ohm 5″ that does then add the additional 2 larger 8ohm speakers for quality sound? I know I’m throwing things at the wall to see what sticks.

    • Hi Dave I’m not sure that I’ll be able to help completely as it seems there are some unknowns in this case. I strongly suspect the system isn’t a direct (standard) type but rather a 70V or other similar system that uses transformers for driving multiple speakers. These are commonly used in buildings & business, both for music speakers or intercom systems as well.

      In principle, I do believe using three 8 Ohms speakers in series would be fine to replace a single 25Ω speaker. However, you’ll definitely want to find out *specifically* what type this system is. 70V (or other systems like it) sometimes uses a transformer at the speaker to convert the amplified signal to one to match that of the speaker used.

      I would find out what you’re working with before going further.

      • No transformers at the satellite stations only the 2 16v 30w transformers at the master station. I could test line voltage but suspect it will be 16vdc. I ordered 2 8 ohm speakers and will look for an 8 ohm 5″ to put into the face plate of the satellite station that can also transmit. I’m hopeful somebody makes a speaker that can transmit in 8 ohms. If not we will still have better sound from the satellite station.

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