Decibel Calculator

Convert between decibel values, voltage/power ratios, and calculate SPL at different distances.

dB to Ratio

Decibels (dB)

Type

Ratio to dB

Ratio

Type

Add dB Levels

Enter dB values separated by commas

SPL Distance Calculator

SPL at reference (dB)

Reference distance (m)

Target distance (m)

How Decibels Work

The decibel (dB) is a logarithmic unit expressing the ratio between two values. For power quantities: dB = 10 log₁₀(P1/P2). For voltage/amplitude: dB = 20 log₁₀(V1/V2). A +3 dB change doubles the power; +6 dB doubles the voltage. Sound pressure level (SPL) decreases by approximately 6 dB each time distance doubles (inverse square law in free field).