Decibel Addition Calculator
Add multiple decibel sound levels together to find the combined noise level with this free acoustics calculator in your browser.
Enter Values
How to use this calculator
- Enter the two source levels in dB.
- Read the combined level.
How it works
Combined = 10 × log₁₀(10^(dB1/10) + 10^(dB2/10)).
Worked example
80 dB + 80 dB. = 83 dB (not 160).
Common mistakes
- Adding decibels directly — they're logarithmic.
- Two equal sources add 3 dB; a source 10 dB quieter barely changes the total.
Frequently asked questions
How do I add decibel levels?
Decibels are logarithmic, so they don't add directly — two equal sources combine to +3 dB, not double the number.
Why do two equal sounds only add 3 dB?
Doubling sound power adds 10 × log10(2) ≈ 3 dB; perceived loudness roughly doubles only around +10 dB.
Why do 80 + 80 dB make 83?
Doubling acoustic energy adds about 3 dB, not double the number — decibels are a log scale.
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Cite this tool
Zerdly. (2026). Decibel Addition Calculator. Retrieved from https://www.zerdly.com/tools/decibel-add-calculator/
Tip: Enter any known values to calculate the remaining results.
Designed to run locally in your browser. Tool inputs are not intentionally stored by Zerdly unless stated otherwise.