Sound System Power Calculator

Work out sound system power instantly with clear inputs, formula shown and shareable results.

About Sound System Power Calculator

Sound pressure falls 6 dB per doubling of distance, so required gain is target level plus 20 log of distance minus speaker sensitivity, and power is ten to the power of that gain over ten. Because power scales logarithmically, the last 6 dB of headroom costs four times the wattage of the average level, which is why amplifiers seem so oversized.

Formulas

Distance loss

loss dB = 20 x log10(distance in metres)

Power required

watts = 10 ^ ((target SPL + distance loss - sensitivity + headroom) / 10)

Worked example

With the default values below, Sound System Power Calculator returns Amplifier power needed with headroom of 453.21. Change any input above and every figure here is recalculated in your browser.

Inputs used

Target sound pressure levelaccepts 40–140 dB: 100 dB
Speaker sensitivity at 1 W, 1 maccepts 60–120 dB: 95 dB
Listening distanceminimum 0.1 m: 6 m
Headroom for peaksaccepts 0–20 dB: 6 dB

Results

Amplifier power needed with headroom: 453.21 W
Power for the average level only: 113.84 W
Level lost over the distance: 15.56 dB
Gain needed above the 1 W rating: 20.56 dB

Step by step

1Values used
2Distance loss
3Power required
4Amplifier power needed with headroom= 453.21 W
5Power for the average level only= 113.84 W
6Level lost over the distance= 15.56 dB
7Gain needed above the 1 W rating= 20.56 dB

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is the Sound System Power figure worked out?

loss dB = 20 x log10(distance in metres). Sound pressure falls 6 dB per doubling of distance, so required gain is target level plus 20 log of distance minus speaker sensitivity, and power is ten to the power of that gain over ten.

Why does this matter?

Because power scales logarithmically, the last 6 dB of headroom costs four times the wattage of the average level, which is why amplifiers seem so oversized.

What do I need to enter?

Enter target sound pressure level, speaker sensitivity at 1 w, 1 m, listening distance, headroom for peaks. The defaults shown are a realistic worked example — swap in your own figures to get a result you can use.