dB Ratio and Percentage Converter
Convert between linear ratios, dB values, and percentage change for voltage, amplitude, and power quantities.
Input
Convert between a linear ratio, dB, and percentage change using amplitude or power equations.
Use voltage/amplitude for voltage gain and signal amplitude. Use power for watts and power gain.
Result
Amplitude and voltage ratios use 20 log10(ratio).
Linear ratios and dB use different views of the same change
This calculator keeps voltage or amplitude ratios separate from power ratios, then shows the matching dB and percentage result.
Amplitude ratios
Use amplitude mode for voltage and signal-amplitude comparisons.
Power ratios
Use power mode for ratios between power quantities.
Percentage view
The percentage result gives a quick linear sense of how far the ratio is from one.
Related calculators
Engineering reference
Equations, assumptions, and design guidance
Converts between a positive linear ratio, decibels, and percentage change using amplitude or power conventions.
Equations and variables
dB = 20 * log10(ratio)dB = 10 * log10(ratio)- ratio
- Linear amplitude or power ratio (dimensionless)
- dB
- Logarithmic ratio (dB)
Assumptions and limitations
Assumptions
- The selected amplitude or power convention matches the quantities being compared.
- Linear ratios are positive.
Limitations
- A signed waveform polarity is not represented by the magnitude ratio.
- Reference-level quantities such as dBm and dBµV require their dedicated conversions.
Worked example and design use
Two-times voltage ratio
Inputs: amplitude ratio = 2
Outputs: level difference is about 6.02 dB, percentage change = 100%
Design guidance
- Confirm whether the source specification uses an amplitude or power ratio before applying the result.