Sound Pressure Level Calculator

Work out sound pressure level instantly with clear inputs, formula shown and shareable results.

About Sound Pressure Level Calculator

Sound pressure level uses 20 log10 rather than 10 log10, because intensity goes with the square of pressure. Against the 20 micropascal reference, 0.2 Pa is 80 dB. That reference is chosen so the pressure and intensity scales read the same number for a plane wave in air.

Formulas

Sound pressure level

L = 20 log10(p / p0)

Reference

p0 = 20 uPa

Worked example

With the default values below, Sound Pressure Level Calculator returns Sound Pressure Level of 80.00. Change any input above and every figure here is recalculated in your browser.

Inputs used

Sound pressureminimum 0 Pa: 0.2 Pa
Reference pressureminimum 0 Pa: 0.00002 Pa

Results

Sound Pressure Level: 80.00 dB
Pressure Ratio: 10,000.0
Equivalent Intensity In Air: 9.5198 × 10⁻⁵ W/m2
Same Pressure In Millipascals: 200.000

Step by step

1Values used
2Sound pressure level
3Reference
4Sound Pressure Level= 80.00 dB
5Pressure Ratio= 10,000.0
6Equivalent Intensity In Air= 0.0001 W/m2
7Same Pressure In Millipascals= 200.000

Assumptions and limits

The result is derived only from the 2 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 4 decimal places, 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

Why 20 log rather than 10 log?

Because intensity is proportional to pressure squared, and the square inside the logarithm becomes a factor of two outside it.

How much pressure is a loud concert?

Around 2 Pa at 100 dB - still only 20 millionths of atmospheric pressure, which shows how sensitive hearing is.