Amplifier, Speaker & SPL Calculator

These calculators will find how loud an amplifier and speaker combination will be, or what size amplifier you need to make a speaker a certain loudness.

There are five factors which contribute to how loud a speaker will be:

1) The distance from the speaker. Sound drops off the further you are away from a speaker.

2) The SPL required. This is how loud you want the sound to be at the distance specified. Some general levels are:

  • 70-80dB  for speech only
  • 80-95dB for light music
  • 95-110dB for heavy music

3) The speaker sensitivity. This is not an indicator of how sensitive the main (human) speaker is, but rather a measurement of the sensitivity of the loudspeaker. It should be available in the specifications for the loudspeaker (see Understanding Speaker Sensitivity for more info).  It is normally stated as the SPL measured 1 metre in front of the speaker with 1 watt of power driving the speaker. Hence the specification will read something like:

Sensitivity (1W/1m) = 85dB

4) Amplifier headroom. This is an allowance for the amplifier to cope with peaks without distortion. At least 3dB headroom is generally recommended. Note that for every 3dB allowance, the power requirement doubles.

5) The power of the amplifier, measured in watts.

In the calculator below, first input the distance from the speaker (and select feet or meters). From this distance the Sound Pressure Level (SPL) loss over that distance is calculated in decibels (dB).

Then, fill in the input fields of either calculator depending on if you want to know the required power for a target SPL (use the first calculator), or if you want to know how loud a given amplifier will be (use the second calculator).

Download Calculator
as Excel File
Prices in US$

Note: these calculations are for “open-air” where there are no reflections from walls, ceiling and/or floors. When reflections are present, the SPL losses can be reduced by up to 6dB.

For those who need to know, the formulas used for these calculations are:

\large{SPL\ loss = {20\times Log_{10}\left(\frac{Distance\, from\, Spkr\left(meters\right)}{1}\right)}


\large{ Amplifier\ power =  \large{10^\frac{required\,amp\,gain}{10}}

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So… in reading your articles each -/+ terminal is essentially an amp. My amp says 2 x 150W/Channel. It has 4 -/+ terminals, two under A Channel, 2 Under B channel. does this mean that each +/- delivers 75w watts. The amp is and Audio Source 310. It also says its bridgeable, which also confuses me. I’m looking to ultimately connect 1 8 ohm subwoofer. (2) 8 ohms speakers and (2) 4 ohm speakers and want to get it it right. Thank you

Hello Sir Geoff, good day…
Im a little confuse understanding about the load of a amplifier..
I hope you can give some of explanation..

My amplifier is sakura 735 700 watts by kensonic,
And the load speaker at the back of the amplifier is,
700Wx2 8 omhs
1300Wx2 4 ohms..
What does it means?

It means that i can put a pair of speaker which is, 500Wx2 4 ohms and,

500Wx2 8 omhs speaker?

Good evening in my place and good day in yours…
I understand now sir, thank for your explanation…really help me a lot..

hello geoff
i am interesting with amplier and speaker but i dont have an idea what to do with my tweeter crown cy 300w 8 ohms parallel to woofer 700w 8 ohms without passive crossover connected to sakura 737 amplier….. i just ask what to do why the tweeter always burning? because the tweete always burning… i think i change my tweetee 6 times…

Hi Geoff
For example if four 200w 8ohm speaker connected in parallel what is the resultant watts and ohm of the speaker system. And if they connected in series what is the resultant watts and ohm.
kindly waiting for your reply
with thanks and regards

Excellent resource, Geoff! Thank you very kindly for your work!
A few questions, if I may…
Do I understand correctly this calculator is set for 8 Ohm speakers?
What if I need to calculate for 4 Ohm speakers? Do I just need to add +3 dB in the “Amplifier Headroom” for 4 Ohm speakers?
For example, if your crest factor is 24 (movies will usually have a crest factor higher than 20 dB and some will go to 24 dB) and you have 4 Ohm speakers, enter 27 into the “Amplifier Headroom” field. Is this correct, please?

Hello Mr Geoff,
I have Elac 101 bookshelf speakers with these specs:nominal 40W/ peakpower handling 55W, impedance 8 oms, recommended amp is 20-100W. Im planning to set these speakers on stands with 4m distance from me. I play blues,jazz,acoustic,movies soundtracks and sometimes dance/house. What power amp to choose, Onkyio A-9211 60W at 8oms, 40W at 4oms or Marantz PM-40 45W? I’ don’t have a clue what is right SPL in my kind of volume. I want pleasant and warm sound and my room is smaller, like an average bedroom.
Thanks in advance 🙂

Hello, I am looking for an amplifier to listen to music only, my speakers are Focus chorus 716 with a sensitivity of 91 db, in the manual recommend using an amplifier between 40 and 200 w, which suggests, thank you very much!

Hey Geoff

I am getting Klipsch SP 280 F speakers (specs at 8ohms@150/600 continuous/peak watts) and having difficulty making decision on receiver that would allow optimal functionality of speakers. Narrowed receivers down to: Marantz SR5011 at 8ohms/100w per channel. Yamaha RX A660 at 8ohms/70 watts per channel (I think), Pioneer Elite VSX 90 at 6ohms/165×7 watts channel. Not really sure what to do. Must the receiver Always match the speaker in ohms and watts? or the speaker match the receiver ohms/watts? I want some headroom too. Distance from components including tv will be about 15 to 20 ft. Thank you.

Hi geoff,
I’m glad i found this site and it will be useful for me. I changed my car radio stereo and install Aftermarket Car Stereo. after this installation the sound was not good, and i found Aftermarket Car Stereo is more powerful and doesn’t match with factory/original speaker.

Aftermarket Car Stereo specifications
55 watts 4 channel of 4 ohms each speaker ,
how much is the power of the speaker that i should buy to improve the sound?
Thank you