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

speaker Ohms calculator section image

HOW TO USE THE SPEAKER OHMS CALCULATOR

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.

Your comments are welcome.
  1. Hi, if i have one voice coil subwoofer 4 ohm (400W RMS) connected to the amp bridged (amp stabil 2 and 4 ohm) so i dont have full power 400W but only 250W… Result is? How much ohm i have?

    Reply
    • Hi, you’ll have 4Ω. The impedance of a speaker doesn’t change based on anything else.

      Only if we wire multiple voice coils/speakers together the *total* Ohms can change. Other than that it’s whatever the speaker impedance is.

      Reply
  2. Hello. I have 2x dual 4 ohm impedance subs. I want to use them with a 1000w Amp. It’s rated at
    4 ohm= 2×250 watts
    2 ohm= 2×500 watts
    Or
    Mono bridged @4ohm =1000w
    I want to use the bridged option, can I do that?
    Or should i use one of the other configurations?

    Reply
    • Hi, there’s no benefit in using the bridged option in this case, plus it will cause more issues due to the speaker impedance not being matched correctly. Wire them for 2Ω each then connect one per channel.

      The power is the same either way.

      Reply
  3. Hi.
    I’m new in the audio world and i have question.
    I have a 2 speakers and sub from Panasonic SC AK750 music system and i want to connect this speakers and sub to PC. I have a music card and DAC (smsl m3) already connected, but this works the best with headphones. My speakers are just desktops creatives z323. Since this Panasonic speakers just lying around i want to somehow connect them. I think i must buy a amplifier which is 3 ohm rating and can provide power to sub? But in my understanding of your calculator, if this one column of speakers are connected in series that total speaker load is 6ohm? Or manufacturer when is saying that it is 3 ohm it means it’s already 3ohm from this 2 pairs of speakers?
    Maybe I’m trying to invent the wheel all over again and the best solution is to sell this whole Panasonic system and buy different speakers? I’m confused.

    Reply
    • Hi, most amplifiers you buy for home audio use will require a minimum of 8 ohms but if you search a lot you may find one compatible with 4 ohms or etc. Yes if you connect speakers in series they add together, however, for 2-way speakers, this causes an issue since crossovers are used and it can change the crossover frequency and can affect the sound.

      If you really want to use the Panasonic speakers the simplest way would be to 1) find a home amplifier (like a mini amp etc.) that can handle down to 2 or 3 ohms, or 2) use a car amplifier with a min. 2 ohm rating. Option #2 will definitely work but will require an AC-DC power supply to power it as well.

      Reply
      • Thanks for quick respond :). So let’s the search for amp begins :D. If in don’t find right amp i just sell this and make new setup :)

        Reply
  4. Hi,

    Great content!

    I’m also new in the audio world and I have question. I have a 2 channel amplifier class D, 200W per channel, at 25 ohms. I’m trying to connect to 4 speakers, 8ohms.

    Just to clarify, if I understood correctly, the only way to do so would be connecting all 4 speakers to only one channel, connected in series. Is that right?

    Thank you very much!

    Reply
    • Hi Paulo. Did you mean “2 ohms”? As 25 ohms doesn’t sound right – at least not for a standard 2-channel stereo amp. Also, it makes a difference what type of speakers you mean: single cone? Coaxial speakers? 2-way speakers? 3-way speakers? Etc.

      Those two things I’ll need to know in order to help. Best regards.

      Reply
  5. It I have 200 watts at .5 ohms and the following loads: 4 ohms, 4 ohms, 4 ohms, 4 ohms, and 1 ohm all in parallel can you tell me the power to each load?

    Thanks!

    Reply
    • Hi Tom. Yes I can, and in fact those numbers will work out nicely to make it pretty simple.

      1. Checking our total Ohms load we have: 1/(1Ω + 1Ω) = 0.5Ω. (We get 1Ω in the first part by 4Ω/4 speakers.)
      2. We know how much power the amp can supply (200W @ 0.5Ω) and in this case we can think of it as two 1Ω loads in parallel to simplify the math then break it down further. We’ll have 100W to each 1Ω as they will share the power.
      3. For the “1Ω load” (4Ω speakers in parallel) we’ll have 100W/4 = 25W each.

      To summarize: 4Ω speakers: 25W each; 1Ω load: 100W. Best regards.

      Reply
  6. Question ? I have an 8 ohm and a 4 ohm speakers wired in series to a series crossover.I then added a 4ohm speaker spliced in directly to positive on one side and negative on other side what’s the impendence over all still 16 ohms ?

    Reply
    • Hi Travis. If I understand your comment correctly, you connected a 4 ohm speaker in parallel with an 8Ω and 4Ω speaker that are in series?

      If that’s the case, you’ll have 12Ω (parallel) 4Ω which we can find by: 1/( 1/12 + 1/4) = 3Ω.

      If however you meant that you just connected it in series with the 8 and 4 ohm speakers, then yes it would be 16Ω.

      Reply
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