Convert sound pressure into decibels using the sound pressure level formula. Enter a pressure value and reference pressure to calculate dB SPL, pressure ratio, sound level category, and calculation steps.
Sound pressure:
Enter the measured sound pressure value. This can be entered in pascals, millipascals, or micropascals.
Reference pressure:
The calculator compares the sound pressure to a reference pressure. For air, the standard reference is commonly 20 µPa.
Conversion:
The calculator converts both values to pascals, finds the pressure ratio, then converts that ratio into dB SPL.
Sound pressure values can be very small, so converting pressure to decibels makes sound levels easier to compare. This is useful for acoustics, microphones, noise checks, speaker testing, audio equipment, engineering, and environmental sound.
The result is a mathematical dB SPL value based on the pressure and reference pressure entered. Real-world measurements can vary based on equipment, distance, background noise, and room conditions.
The standard formula for converting sound pressure to dB SPL is:
dB SPL = 20 × log10(p ÷ p₀)
To convert sound pressure to dB SPL, divide the sound pressure by the reference pressure, take log10 of the ratio, then multiply by 20.
For sound in air, the common reference pressure is 20 micropascals. For underwater sound, 1 micropascal is commonly used.
Sound pressure is an amplitude-style measurement, so pressure ratio calculations use 20 × log10. Power and intensity ratios use 10 × log10.
Yes, when sound pressure is compared to a reference pressure, the result is usually called sound pressure level, or dB SPL.