Skip to content
Calculation Machine

Sones to dBA Estimate Calculator

Approximate A-weighted sound level from a sone rating.

Reviewed by the Calculation Machine team · How we check our maths

Your values

ⓘ Live results

Results
Estimated sound level
59.4 dBA
Perceived loudness
Quiet bathroom fan

Quick answer

As a rule of thumb, dBA is approximately 33.2 times the log base 2 of sones, plus 40, though the exact relationship depends on spectrum.

The formula

dBA ~ 40 + 33.22 x log2(sones)

Worked example

Worked example

Using the values the calculator loads with.

Inputs

  • Fan sone rating1.5 sones

Result

  • Estimated sound level59.4 dBA
  • Perceived loudnessQuiet bathroom fan

How to use the Sones to dBA Estimate Calculator

  1. 1Enter the fan's sone rating from its spec sheet (bath fans are commonly rated 0.5-4 sones).
  2. 2Read the approximate equivalent A-weighted decibel level.
  3. 3Use as a rough guide only — true dBA depends on the frequency spectrum of the specific fan.

Frequently asked questions

Why is this only approximate?

Sones measure perceived loudness while dBA measures pressure with frequency weighting; the two scales relate non-linearly and depend on spectral content.

What sone rating is 'quiet' for a bath fan?

1.0 sone or less is generally considered quiet for residential bathroom fans.

About this calculator