Decibel Converter
Convert between decibels and ratios. Decibels express how much bigger or smaller one power, voltage or sound level is compared with another.
How to use the Decibel Converter
- Choose the conversion direction and whether it is a power or a voltage ratio.
- Enter the ratio or the dB value.
- Read the result.
How it works
Decibels are logarithmic. For power: dB = 10 × log₁₀(P₂/P₁). For voltage, current or sound pressure (amplitudes): dB = 20 × log₁₀(V₂/V₁), because power is proportional to the square of amplitude. So +3 dB ≈ double the power, +6 dB ≈ double the voltage, and +10 dB is ten times the power — which most people hear as roughly twice as loud.
Decibel table
| dB | Power ratio | Voltage ratio |
|---|---|---|
| -20 | 0.01 | 0.1 |
| -10 | 0.1 | 0.3162 |
| -6 | 0.2512 | 0.5012 |
| -3 | 0.5012 | 0.7079 |
| 0 | 1 | 1 |
| +3 | 1.9953 | 1.4125 |
| +6 | 3.9811 | 1.9953 |
| +10 | 10 | 3.1623 |
| +20 | 100 | 10 |
| +30 | 1,000 | 31.6228 |
Frequently asked questions
What is 3 dB in power?
About double (×1.995).
What is 6 dB in voltage?
About double the voltage (×1.995) — four times the power.
How much louder is 10 dB?
Ten times the sound power, perceived as roughly twice as loud.
What is 0 dB?
A ratio of 1 — no change. In sound level (dB SPL) it is the reference threshold of hearing.