SPL Distance Calculator
A free, browser-based calculator. Runs entirely in your browser — no sign up, nothing stored.
100% FreeRuns in your browserBasic
Enter Values
Enter your values and press Calculate to see results.
How to use this calculator
- Enter the known SPL and distance, then the new distance.
- Read the SPL at the new distance.
How it works
Level change = 20 × log10(new distance ÷ old distance). Doubling distance drops 6 dB.
Worked example
100 dB at 1 m → 4 m. ≈ 88 dB (−12 dB).
Common mistakes
- Applying it indoors — reflections make real rooms differ from free-field.
- Using a line source (this assumes a point source).
Frequently asked questions
Why 6 dB per doubling?
Sound energy spreads over a sphere; the inverse-square law gives a 6 dB drop each time distance doubles.
Related tools
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.