Decibel Calculator
Choose a ratio model and supply positive measured and reference values in the same unit. Voltage is an amplitude ratio.
A QUICK WALKTHROUGH
How to use this tool
- Choose amplitude, power, sound pressure or a supplied digital reference.
- Enter both values in one matching unit; optionally name that unit.
- Calculate; power mode includes the linear ratio. Copy or download the full input and result report.
Scope
Amplitude and voltage use 20 log₁₀; power uses 10 log₁₀. Voltage implies the same power ratio only at equal impedances. Standard air dB SPL requires an entered reference equivalent to 20 µPa in the matching pressure unit. dBFS requires your supplied full-scale reference. Labels do not establish calibration.
Linear power ratio P₂/P₁ (unitless)
Power mode also reports measured power P₂ divided by reference power P₁ as a unitless linear ratio. The dB result uses the difference of logarithms. An unrepresentable linear ratio is reported explicitly and does not invalidate a representable dB result.
GOOD TO KNOW
Common questions
Are these equipment specifications?
No. These results describe the stated mathematical model and user inputs.
Why can dB be shown when the linear ratio cannot?
The logarithm difference avoids overflowing or underflowing the division P₂/P₁. The report marks the linear ratio as unrepresentable instead of reporting zero or infinity.