Speaker Wattage
Estimate the speaker power needed to hit a target SPL at a distance.
About Speaker Wattage
Each doubling of amplifier power adds about three decibels, so the needed watts grow by ten times per ten-decibel target step, adjusted for distance loss. Undersized speakers compress and distort at high levels; picking watts from an SPL plan keeps the sound clean for the whole room.
Formula
Speaker Wattage
Watts = 10^((target SPL - sensitivity + 20 x log10(distance)) / 10)
- SPL
- Sound pressure level in decibels, the loudness at the listener
Worked example
With the default values below, Speaker Wattage returns Power Needed of 179.6. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Sensitivityaccepts 80–100 dB @ 1W/1m
- 87 dB @ 1W/1m
- Target levelaccepts 80–120 dB SPL
- 100 dB SPL
- Distanceaccepts 0.5–100 m
- 3 m
Results
- Power Needed
- 179.6 W
- Level at Distance
- 77.5 dB SPL
- Recommended With Headroom
- 359 W
Step by step
- 1Values used
- 2Speaker Wattage
- 3Power Needed= 179.6 W
- 4Level at Distance= 77.5 dB SPL
- 5Recommended With Headroom= 359 W
Assumptions and limits
- The result is derived only from the 3 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 1 decimal place, 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 Speaker Wattage calculated?
Watts = 10^((target SPL - sensitivity + 20 x log10(distance)) / 10) Each doubling of amplifier power adds about three decibels, so the needed watts grow by ten times per ten-decibel target step, adjusted for distance loss.
Why does Speaker Wattage matter?
Undersized speakers compress and distort at high levels; picking watts from an SPL plan keeps the sound clean for the whole room.
What values do I need to enter?
This calculator takes 3 inputs: Sensitivity, Target level, Distance. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.