redzilla
All tools

IP Addressing

Layer 2

Cabling

Performance

Wireless

CCTV

Optical fiber

Power

Datacenter

AV

Voice

Diagnostics

Calculation

Security

AV

Speaker SPL

Calculate the sound pressure level (dB SPL) of a speaker at a distance from its sensitivity (dB @1 W/1 m) and the applied power, or solve for the power or the distance needed for a target SPL. Free-field model (no reverberation), with −6 dB per doubling of distance. Everything in your browser.

What do you want to find?
dB

From the datasheet: SPL the speaker produces with 1 W measured at 1 m. Typical HiFi 85–90, PA 95–100+.

W

Every time you double the power you gain +3 dB. 10× the power = +10 dB.

m

In free field, every time you double the distance the level drops −6 dB (inverse-square law).

Examples
redzilla.cl — spl 
 
  
 
 
SPL at distance
 
—
 
—
 
 
 
Max SPL · @1 m
 
—
 
at the applied power
 
 
 
Distance loss
 
—
 
relative to 1 m
 
 
  
 
 SPL @d —  
 
 SPL @1 m —  
 
 Result —  
 
  
 
SPL by distance
 
 
  
DistanceSPLvs 1 m
   
 
 
  current distance · every time the
          distance doubles the level drops 6 dB.

 
 
 How it is calculated · SPL, power and distance 
 
 1. Free-field SPL at distance
d (in meters):
SPL = sensitivity + 10·log₁₀(P) − 20·log₁₀(d), with
P in watts. Sensitivity is the SPL at
1 W and 1 m.

 
 2. Power: each doubling gives
+3 dB → 10·log₁₀(P). Distance: each
            doubling subtracts −6 dB → −20·log₁₀(d)
(inverse-square law).

 
 3. Solve the power for a
            target SPL at distance d:
P = 10^((target − sens + 20·log₁₀(d)) / 10).

 
 4. Solve the distance for
            a target SPL at power P:
d = 10^((sens + 10·log₁₀(P) − target) / 20).

 
 5. Free-field model
            (outdoors or an anechoic chamber): it ignores reverberation, room
            reflections and air absorption. Indoors the real SPL is usually
            higher because of reflections. It does not account for the speaker's
            distortion or its maximum power handling.

 
 
 
 
 
Runs locally in your browser · no sign-up · nothing leaves your browser.
  
 
 
How it works
 
The calculator estimates the sound pressure level (dB SPL) a loudspeaker delivers at a given distance, from two datasheet values: the sensitivity (dB measured with 1 W at 1 m) and the applied power in watts. It also works in reverse: it solves for the power needed to reach a target SPL at some distance, or for the maximum distance at which that target is met with a given power.
The formula is the free-field one: SPL = sensitivity + 10·log₁₀(P) − 20·log₁₀(d). Doubling the power adds +3 dB and doubling the distance subtracts −6 dB (inverse square law). The model does not include reverberation or room reflections: indoors the actual level is usually somewhat higher, and it does not account for the maximum power the speaker can handle either.
 
 
Example: 96 dB PA speaker with 200 W at 15 m
 
     
  1. Power gain: 10·log₁₀(200) = +23.0 dB, so at 1 m the speaker delivers 96 + 23.0 = 119.0 dB SPL.
  2. Distance loss: 20·log₁₀(15) = 23.5 dB.
  3. SPL at the listening position: 119.0 − 23.5 ≈ 95.5 dB SPL at 15 m, a loud but reasonable level for sound reinforcement.
    4.  
 
 
 
 
Frequently asked questions
 
 
 How many dB do you lose as you move away from the speaker? 
In free field the level drops 6 dB every time the distance doubles: from 1 m to 2 m you lose 6 dB, at 4 m it is already 12 dB and at 8 m it is 18 dB. The general formula is 20·log₁₀ of the distance in meters. Indoors the actual drop is smaller because room reflections add energy.
 
 How much power do I need to get 10 dB more volume? 
Ten times more power: going from 50 W to 500 W adds +10 dB, while doubling the power only adds +3 dB. That is why choosing a speaker with 6 dB more sensitivity is often more efficient than buying an amplifier four times more powerful.
 
 What does speaker sensitivity (dB @1 W/1 m) mean? 
It is the SPL the speaker produces when fed 1 W, measured at 1 m, and it is the starting point of the whole calculation. A typical HiFi speaker sits around 85 to 90 dB, while a professional PA speaker reaches 95 to over 100 dB. At the same power, 3 dB more sensitivity is equivalent to doubling the amplifier.
 
 Is the result valid indoors with reverberation? 
As a reference, yes, but the model is free field (outdoors or an anechoic chamber): it ignores reflections, reverberation and air absorption. In a real room the measured SPL is usually higher than the calculated one, especially far from the speaker. Everything runs in your browser, with no data sent to any server.
 
 
 
  
   
 Was this tool useful? 
      
   
 
 
 Disclaimer We take great care to keep every tool accurate and review it thoroughly; even so, we can't guarantee it is free of errors or take responsibility for how the results are used. We recommend double-checking anything critical. 
 Found an error? Let us know →