Decibel Calculator

Add sound levels correctly (energy sum), convert dB to linear ratios and sound pressure, and compare real-world loudness.

Add Sound Levels

Enter any number of dB values. The total uses the correct energy sum: 10·log₁₀(Σ 10^(L/10)).

L1dB
L2dB
Total: 73 dB(naive sum would be 140 dB - wrong)

dB Conversions

dB

Power ratio (10^(dB/10))

2,511,886,431.5096×

Pressure/amplitude ratio (10^(dB/20))

50,118.7234×

Sound pressure (dB SPL → Pa)

1.002374 Pa

Closest everyday sound: Chain saw, heavy traffic (90 dB)

Loudness Reference

0
Threshold of hearing
20
Whisper, rustling leaves
30
Quiet library
40
Whisper from 1 m, light rainfall
50
Quiet residential area
60
Normal conversation
70
Vacuum cleaner, busy office
80
Lawn mower, busy traffic
85
OSHA exposure limit (8 h)
90
Chain saw, heavy traffic
100
Power mower close, siren at 30 m
110
Rock concert, jackhammer
120
Pain threshold begins
130
Airplane takeoff at close range
140
Jet engine at 30 m, rocket launch

Red bars: levels where prolonged exposure causes hearing damage (OSHA limit 85 dB).

Quick Answer

Decibels are logarithmic, so you cannot add them like ordinary numbers. Two identical 60 dB sources produce 10·log₁₀(2) ≈ 63 dB, not 120 dB. To combine N levels: total = 10·log₁₀(Σ 10^(Lᵢ/10)). A 3 dB increase means twice the sound energy; a 10 dB increase means ten times the energy and sounds roughly twice as loud to most people. This calculator adds any number of levels with the correct energy sum, converts dB to linear power and pressure ratios, and shows where everyday sounds sit on the scale.

Key Facts

  • dB is logarithmic: 3 dB = 2× energy, 10 dB = 10× energy
  • Two equal sources: total = L + 3 dB (not 2×L)
  • 10 dB increase ≈ sounds twice as loud to human ears
  • 0 dB SPL is the threshold of human hearing (1,000 Hz)
  • 94 dB SPL = 1 pascal of sound pressure (the standard reference)
  • Conversation ≈ 60-65 dB; city traffic ≈ 85 dB; rock concert ≈ 110 dB
  • Continuous exposure above 85 dB can damage hearing over time

Frequently Asked Questions

No. Decibels are log scale. Adding 70 dB + 70 dB gives 73 dB, not 140 dB. The correct formula sums the underlying energies: L_total = 10·log₁₀(10^(L1/10) + 10^(L2/10) + …). The calculator does this for any number of sources.

10 dB is ten times the sound energy, and to most listeners it sounds about twice as loud. 3 dB (double the energy) is just barely noticeable. 20 dB is 100× the energy and sounds roughly four times as loud.

dB is a generic ratio unit. dB SPL measures sound pressure relative to 20 micropascals (the hearing threshold). dB(A) applies a frequency weighting that approximates how the human ear hears, reducing the weight of very low and very high frequencies - this is what noise meters and regulations usually report.

Below 70 dB for unlimited exposure. OSHA limits occupational exposure to 85 dB for 8 hours; every additional 3 dB halves the safe time. At 100 dB (loud concert) safe exposure drops to about 15 minutes per day. Use ear protection above 85-90 dB.

p = 20×10⁻⁶ · 10^(L/20) pascals, where L is dB SPL. So 94 dB SPL = 1 Pa, 60 dB ≈ 0.002 Pa, 120 dB ≈ 20 Pa. The calculator includes this conversion.

Pain threshold sits around 120-130 dB SPL. Above that, the sound pressure physically overdrives the eardrum and inner-ear hair cells. 85 dB is 10^(85/10) = 31.6 million times the reference energy - intense, but far below the damage threshold for short exposures.