About the dB Calculator
What is the dB Calculator?
Decibels express ratios on a logarithmic scale. This decibel calculator converts power ratios (10 log) and voltage or sound-pressure ratios (20 log) to dB and back.
It also adds sound levels correctly: two 90 dB machines make 93 dB, not 180 dB.
How to use the dB Calculator
- Calculation (sample: Power ratio → dB (10 log))
- Reference Value (P₁ or V₁) or dB (sample: 1)
- Measured Value (P₂ or V₂) (sample: 100)
- Sound Levels to Add (dB, separated by commas) (sample: 85, 85)
- Press Calculate Decibels (results also refresh as you type). The result card shows the Result, along with Ratio and Formula.
Formula used
dB = 10 × log₁₀(P₂ ÷ P₁) = 20 × log₁₀(V₂ ÷ V₁)
- Adding levels = L = 10 × log₁₀(Σ 10^(Lᵢ ÷ 10))
+3 dB doubles power; +10 dB is perceived as roughly twice as loud.
Worked example
These are the sample values already filled in the calculator above, and the result it returns for them:
| Input | Sample value |
|---|---|
| Calculation | Power ratio → dB (10 log) |
| Reference Value (P₁ or V₁) or dB | 1 |
| Measured Value (P₂ or V₂) | 100 |
| Sound Levels to Add (dB, separated by commas) | 85, 85 |
| Result | Value |
|---|---|
| Result | 20 dB |
| Ratio | 100× |
| Formula | 10 × log₁₀(value₂ ÷ value₁) |
Tips for using the dB Calculator
- Indian noise rules limit residential areas to 55 dB(A) by day and 45 dB(A) at night.
- Hearing protection is recommended above 85 dB(A) over an 8-hour day; the Factories Act limit is 90 dB(A).