The decibel is a logarithmic scale that matches how we hear: every +10 dB sounds roughly twice as loud and carries ten times the intensity. A quiet room is about 30 dB, conversation 60 dB, and sounds above 85 dB can damage hearing over time.
How to use the Decibel Calculator
- Calculate from
- Sound pressure p
- Sound intensity I (W/m²)
- Sound level (dB)
- Measurement distance r₁
- New distance r₂
Results update as you type, every field has its own unit menu, and everything is calculated in your browser.
How it works
Choose whether you know the sound pressure or intensity, or type a level in dB into the result. Add the distances to see how loud the sound is farther away.
Inputs explained
| Field | What to enter |
|---|---|
| Calculate from | Choose one: Sound pressure p, Sound intensity I, Sound level in dB |
| Sound pressure p | Units: Pa, mPa, µPa |
| Sound intensity I (W/m²) | A number |
| Sound level (dB) | A number |
| Measurement distance r₁ | Units: m, cm, mm, km, in, ft … |
| New distance r₂ | Units: m, cm, mm, km, in, ft … |
What each result means
- Sound pressure = 2e-5×10^([Sound level]÷20)
- Sound intensity = 1e-12×10^([Sound level]÷10)
- Level at distance r₂ (point source) = [Sound level] – 20×log10([New distance r₂]÷[Measurement distance r₁])
Example values
How the main result changes when Sound pressure p changes and everything else stays at the example values above:
| Sound pressure p (Pa) | Sound level (dB) |
|---|---|
| 0.01 | 53.979 |
| 0.015 | 57.501 |
| 0.02 | 60 |
| 0.025 | 61.938 |
| 0.03 | 63.522 |
| 0.04 | 66.021 |
Formula
L_p = 20·log₁₀(p/p₀), p₀ = 20 µPa · L_I = 10·log₁₀(I/I₀), I₀ = 10⁻¹² W/m²
L₂ = L₁ − 20·log₁₀(r₂/r₁)
Worked example
Inputs: Calculate from: Sound pressure p; Sound pressure p: 0.02 Pa; Measurement distance r₁: 1 m; New distance r₂: 10 m.
Results: Sound level = 60 dB; Sound pressure = 0.02 Pa; Sound intensity = 1.0000e-6 W/m²; Level at distance r₂ (point source) = 40 dB; Comparable to = Quiet office.
Key terms
- Sound pressure level
- Logarithmic measure of sound pressure relative to 20 µPa.
Frequently asked questions
How much louder is 10 dB?
Ten times the intensity, about twice as loud to the ear.
What is the reference pressure?
20 µPa, the threshold of human hearing at 1 kHz.
How fast does sound fade with distance?
About 6 dB per doubling of distance from a point source outdoors.
When does noise damage hearing?
Long exposure above 85 dB(A) is a risk; above 120 dB can harm instantly.