🔊Decibel Calculator

Convert between decibels and a power or amplitude ratio — enter either value.

Ratio Type

Decibels (dB)

Ratio (P/P₀ or A/A₀)

Free Decibel Calculator

This decibel calculator converts between a decibel value and the underlying ratio it represents, in either direction. For power or intensity ratios (like sound intensity or electrical power), dB = 10·log₁₀(ratio). For amplitude or pressure ratios (like sound pressure or voltage), dB = 20·log₁₀(ratio) — the factor of 20 accounts for power being proportional to amplitude squared.

Leave either the dB or ratio field blank to solve for it. Every 10 dB (power) or 20 dB (amplitude) represents a 10× change in the ratio — a useful mental shortcut for working with the logarithmic decibel scale.

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