Rex says
Everyday utility math — the kind you'd otherwise pull up four browser tabs for. I keep it to one clean answer.
Try a scenario
Click to load — tweak from there.Inputs
Result
Estimated SPL at listener
106.0
Total dB lost over distance
26.0
dB lost per distance doubling (free field)
6
Psst — share this and help Rex grow
One click, a permanent link with your numbers baked in.
How to use this
- 1Enter rated spl at reference distance (dB).
- 2Enter reference distance (m).
- 3Enter distance to listener (m).
- 4Read your estimated spl at listener on the right — it updates as you type.
- 5Hit Share to keep the scenario or send it to someone.
About this calculator
Sound pressure level (SPL) drops with distance according to the inverse square law in free field — roughly 6 dB for every doubling of distance outdoors, though indoor reverberant spaces lose less due to reflections. This calculator takes a speaker's rated SPL at a reference distance (usually 1 meter, printed on the spec sheet) and projects the level at your actual mix position or back-of-room distance, which is the real number that determines whether your PA is loud enough where it counts.
Worked example
Using the values the calculator loads with:
Inputs
- Rated SPL at reference distance: 132 dB
- Reference distance: 1 m
- Distance to listener: 20 m
Results
- Estimated SPL at listener: 106
- Total dB lost over distance: 26
- dB lost per distance doubling (free field): 6
What each field means
Inputs
- Rated SPL at reference distance (dB)
- The rated spl at reference distance used in the calculation, measured in dB. Starts at 132 dB so you have a working example on load. Accepted range: 60–160 dB.
- Reference distance (m)
- The reference distance used in the calculation, measured in m. Starts at 1 m so you have a working example on load.
- Distance to listener (m)
- The distance to listener used in the calculation, measured in m. Starts at 20 m so you have a working example on load.
Results
- Estimated SPL at listener
- Returned as a decimal number and shown as the headline result. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Total dB lost over distance
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- dB lost per distance doubling (free field)
- Returned as a whole number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
Why 6 dB per doubling of distance and not something else?
The inverse square law states sound intensity falls off with the square of distance in a free field, which works out to a 6 dB drop in SPL every time you double the distance from the source. Indoors, reflected sound partially compensates, so real-world loss is often closer to 3-4 dB per doubling in reverberant rooms.
What SPL level is safe for an audience over a full show?
OSHA and hearing-health guidelines generally recommend average levels under 100-105 dB for extended exposure without hearing protection, with peak levels ideally not exceeding 115 dB even briefly. Mix engineers commonly target 95-102 dB average at front-of-house for live rock shows.
Does this formula account for outdoor wind and humidity?
No — this is the idealized free-field inverse square model. Wind, humidity, temperature gradients, and ground absorption all add extra attenuation outdoors, especially at high frequencies over long distances, so treat the result as a best-case estimate for outdoor shows.
Accuracy and limitations
- Estimates assume standard, average conditions — local rules, pricing, and materials vary.
- Results are rounded for readability; add a buffer before ordering, booking, or committing.
- Double-check anything with a real cost attached against a local quote.
Related tools
Cite this calculator
Writing about this topic? Grab a citation — every link helps keep these tools free.
RevenueLab. (2026). Speaker SPL Distance Calculator. Retrieved from https://www.revenuelab.fyi/toolbox/speaker-spl-distance
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/speaker-spl-distance" target="_blank" rel="noopener">Speaker SPL Distance Calculator — RevenueLab</a> (2026).</p>
Source: [Speaker SPL Distance Calculator — RevenueLab](https://www.revenuelab.fyi/toolbox/speaker-spl-distance) (2026).