Convert dB SPL to pascals and pascals to dB SPL instantly. Type in any box and every other unit updates: pascals, micropascals, sound intensity and peak pressure, plus microphone sensitivity in mV/Pa, dBV and dBFS. The working is shown for every result. Remember: 94 dB SPL is about 1 pascal.
SPL Converter
Type in any box: every other unit updates instantly. The working is shown under the result.
94 dB SPL = 1.002 Pa
L = 20 × log10(p / p₀) = 20 × log10(1.002 Pa / 20 µPa) = 94 dB SPL
Sound intensity level: 93.86 dB re 1 pW/m². Intensity: 0.002431 W/m². In psi: 1.454 × 10⁻⁴.
Close to: microphone calibrator (1 Pa), 94 dB SPL.
dBV is re 1 V; dBu is re 0.775 V. Datasheets state sensitivity at 1 kHz and 94 dB SPL (1 Pa).
Reference values (air, 20 µPa)
Select a row to load it into the converter.
| dB SPL | Pressure | Example |
|---|---|---|
| 20 µPa | Threshold of hearing | |
| 200 µPa | Rustling leaves | |
| 2 mPa | Quiet library | |
| 20 mPa | Normal conversation | |
| 100.237 mPa | Older microphone datasheets (0.1 Pa) | |
| 200 mPa | Heavy traffic | |
| 1.002 Pa | Microphone calibrator (1 Pa) | |
| 2 Pa | Car horn at 5 m | |
| 10.024 Pa | Calibrator high setting (10 Pa) | |
| 20 Pa | Siren up close, threshold of discomfort | |
| 63.246 Pa | Threshold of pain | |
| 200 Pa | Jet engine at 30 m | |
| 100,237 Pa | One atmosphere: the largest undistorted sound in air |
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What Is SPL (Sound Pressure Level)?
Sound is a tiny, fast change in air pressure. Sound pressure is the size of that change, measured in pascals (Pa) as an RMS value. Sound pressure level (SPL) expresses the same pressure on a logarithmic scale in decibels, compared with a reference of 20 micropascals (20 µPa), roughly the quietest 1 kHz sound a young, healthy ear can detect. That is why 0 dB SPL is the threshold of hearing, not silence.
The pressures involved are extremely small: normal conversation at 60 dB SPL is only 0.02 Pa, while the air around you is at about 101,325 Pa. The decibel scale squeezes this huge range, a million to one between hearing threshold and pain, into numbers from 0 to about 130. Read more in our guides to sound pressure level and what a decibel is.
dB to Pascal and Pascal to dB Formulas
The converter uses the standard definitions (IEC 60050 and ISO 80000-8):
- Pascal to dB SPL: L = 20 × log10(p ÷ p₀), with p₀ = 20 µPa = 0.00002 Pa.
- dB SPL to pascal: p = p₀ × 10^(L ÷ 20).
The factor is 20, not 10, because pressure is a field quantity: sound intensity and power grow with the square of pressure, and 10 × log10(p²) = 20 × log10(p). The logarithmic decibel scale guide explains this in more detail. Three worked examples:
- 94 dB SPL to Pa: 0.00002 × 10^(94 ÷ 20) = 0.00002 × 50,119 = 1.002 Pa. This is why acoustic calibrators produce 94 dB: it is almost exactly 1 Pa.
- 0.2 Pa to dB SPL: 20 × log10(0.2 ÷ 0.00002) = 20 × log10(10,000) = 80 dB SPL, about the level of heavy traffic.
- 120 dB SPL to Pa: 0.00002 × 10^6 = 20 Pa, the level of a siren up close (see is 120 dB loud?).
Decibel Rules of Thumb
| Change in level | Sound pressure | Sound intensity (energy) | Perceived loudness |
|---|---|---|---|
| +3 dB | × 1.41 | × 2 | Just noticeable |
| +6 dB | × 2 | × 4 | Clearly louder |
| +10 dB | × 3.16 | × 10 | About twice as loud |
| +20 dB | × 10 | × 100 | About four times as loud |
| +40 dB | × 100 | × 10,000 | About 16 times as loud |
So doubling the sound pressure adds 6 dB, while doubling the power or the number of equal sources adds only 3 dB. Loudness follows the ear, not the physics: roughly twice as loud for every 10 dB.
SPL, Sound Intensity and Sound Power
Sound intensity is the energy flowing through a square metre, in W/m². For a plane wave in air, I = p² ÷ 413, and the sound intensity level re 1 pW/m² is almost identical to the SPL (within about 0.1 dB), which is why the two are often used interchangeably. Sound power level (Lw, dB re 1 pW) is different: it describes how much sound a machine emits in total, whatever the distance, and appears on appliance and machinery labels. SPL is what you measure at a particular spot, and it falls as you move away.
For the full family of decibel units, from dBm and dBW to dBu and dBV, see dB vs dBm vs dBW and the decibel units guide.
dB SPL vs dBA, dBFS and dBV
- dB(A) is SPL with A-weighting, which reduces low and very high frequencies to match human hearing. A sound level meter set to A shows dB(A); the pressure conversion works the same way for the weighted value. See dB vs dBA.
- dBFS is a digital level relative to the loudest value a recorder or sound card can store (0 dBFS). It has no fixed link to SPL until you know the microphone’s sensitivity; dB vs dBFS explains how they relate.
- dBV and dBu are voltages relative to 1 V and 0.775 V. Microphone datasheets give sensitivity as mV/Pa or dBV/Pa at 94 dB SPL, which the microphone tab of the converter translates into output voltage.
Example: a MEMS microphone with a sensitivity of −26 dBFS reads −26 dBFS at 94 dB SPL, so it reaches full scale (0 dBFS) at 120 dB SPL. Louder sounds clip. That is one reason phone meters struggle above about 110–120 dB.
Underwater Sound: Why dB re 1 µPa Is Different
Underwater acoustics uses a reference pressure of 1 µPa instead of 20 µPa. The same pressure therefore reads 26 dB higher in water (20 × log10(20) = 26.02 dB). The media also differ: water’s acoustic impedance is about 3,600 times that of air, so for the same sound intensity the underwater level in dB re 1 µPa is roughly 61.5 dB higher. Comparing a “150 dB” ship noise figure with a “150 dB” jet engine without these corrections is a common mistake. Choose Water in the converter to work with dB re 1 µPa.
Can You Convert Hz to dB?
No. Hertz (Hz) measures frequency, meaning how high or low a sound is, while decibels measure level, meaning how strong it is. A 100 Hz hum and a 5,000 Hz whistle can both be 70 dB. What you can do is measure the level at each frequency with a frequency analyzer, or play a chosen frequency at a chosen level with the tone generator. See dB vs Hz for the full explanation.
How to Measure SPL
A sound level meter measures SPL directly. A phone or laptop with the free sound decibel meter gives a good estimate once you calibrate the microphone against a known source, ideally a 94 dB (1 Pa) calibrator. For legal or workplace measurements you need a Class 1 or Class 2 instrument; sound level meter vs decibel meter compares them, and online decibel meter accuracy explains what to expect from a phone.
Frequently Asked Questions
How many pascals is 94 dB?
94 dB SPL is 1.002 Pa, usually rounded to 1 Pa. 114 dB SPL is 10 Pa.
What is 0 dB SPL in pascals?
0 dB SPL is 20 µPa (0.00002 Pa), the reference pressure and roughly the threshold of human hearing at 1 kHz.
How do I convert pascals to decibels?
Divide the pressure by 0.00002, take log10 and multiply by 20. For 2 Pa: 20 × log10(100,000) = 100 dB SPL.
Is SPL the same as loudness?
No. SPL is a physical measurement. Loudness is how loud a sound seems, which depends on frequency and is measured in phons and sones; a 50 Hz tone needs far more SPL than a 1 kHz tone to sound equally loud.
What is the highest possible SPL?
About 194 dB SPL in air at sea level, where the pressure swing equals atmospheric pressure. Above that, the wave becomes a shock wave. The threshold of pain is around 130 dB SPL (about 63 Pa); see is 130 dB loud?