Decibel (dB) Calculator
Convert power or voltage ratios to decibels and back; also dBm ↔ watts.
How to use the Decibel
- Enter or select: Quantity.
- Fill in what you know of: Ratio, Decibels — leave the unknown empty.
- The results (Ratio, Decibels, If ratio is power in mW) are calculated instantly as you type.
- Use “Copy link” to share the calculation with the same input values.
Formula
- Power: dB = 10·log₁₀(P₂/P₁)
- Voltage: dB = 20·log₁₀(V₂/V₁)