Decibel Calculator
Calculate the ratio between two levels in decibels. This free online science & engineering calculator runs entirely in your browser — no signup, no data sent anywhere.
Inputs
Results
How It Works (Formula & Method)
Decibels express a ratio on a logarithmic scale. For power quantities, dB = 10·log₁₀(P₂/P₁); for field quantities like voltage, dB = 20·log₁₀(V₂/V₁). Every 10 dB is a 10× change in power; every 3 dB roughly doubles it.
Worked Example
Below is a worked example using the calculator's default values. The same numbers are pre-filled in the form above so you can press Calculate and see the result without typing anything.
Inputs used:
- Reference Value: 1
- Measured Value: 100
- Quantity Type: power
With these inputs, the calculator computes the metrics shown in the Results panel. Change any value and press Calculate again to see how the result responds — the live widget and the chart both update instantly.
Frequently Asked Questions
What does the Decibel Calculator compute?
The Decibel Calculator takes 3 input values and returns 2 results. Calculate the ratio of two power or voltage levels in decibels (dB) using the standard logarithmic formulas.
Is my data sent to a server?
No. The Decibel Calculator runs entirely in your browser using static JavaScript. Your inputs are never transmitted to CalculatorHive or any third party, and nothing is stored after you close the page.
Is this calculator free to use?
Yes. Every calculator on CalculatorHive is completely free. There is no signup, no paywall, and no usage limit. The site is supported by display advertising and affiliate partnerships, which are clearly labeled.
How accurate is the result?
The math is mathematically exact for the inputs you provide. Real-world accuracy depends on how accurately your inputs reflect the real situation — defaults are typical values, not guarantees.