What is the difference between power ratio and voltage ratio?

Power ratio uses the formula: dB = 10 × log₁₀(P₂/P₁). Voltage (amplitude) ratio uses: dB = 20 × log₁₀(V₂/V₁). The factor of 2 difference comes from the fact that power is proportional to voltage squared.

Why does 3 dB correspond to roughly a 2× power ratio?

10 × log₁₀(2) ≈ 3.0103 dB. This is why "−3 dB point" means half-power in filter and amplifier specs.

0 dB means the ratio is exactly 1 (no gain or loss). For power: 10^(0/10) = 1. For voltage: 10^(0/20) = 1.

Can dB values be negative?

Yes. Negative dB means attenuation (ratio < 1). For example, −6 dB voltage means the output is half the input amplitude (ratio = 0.5).

What ratio types apply in audio engineering?

Audio engineers almost always use the voltage/amplitude ratio (20 log rule) because voltage is measured directly at input and output terminals, not power.

dB to Ratio Converter

Name: dB to Ratio Converter
Availability: InStock
Author: Nham Vu

Convert between decibels (dB) and power or voltage/amplitude ratios instantly — forward and reverse.

Conversion Settings

Direction

Ratio Type

dB Value

Enter the decibel value to convert to a ratio.

Formula

ratio = 10 ^ (dB / 10)

Result

Enter a value on the left to see the result.

Ratio

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Quick Reference

dB	Power Ratio	Meaning

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