Decibel Calculator

Use this decibel calculator to convert between dB values and ratios or to combine two sound levels. Decibels are logarithmic, so they are useful for comparing power, intensity, pressure, audio gain, and noise levels across large ranges.

How to use this calculator

Choose dB to ratio, Ratio to dB, or Combine levels. For ratio conversions, choose Power/intensity ratio or Amplitude/pressure ratio. Enter the dB value, ratio, or two sound levels. The result shows the converted ratio, decibel value, or combined level.

Formula

For power or intensity ratios, the relationship is commonly:

dB = 10 x log10(power ratio)

For amplitude or pressure ratios under comparable conditions, the multiplier is 20 instead of 10. Combining levels uses linear intensity first:

$combined = 10 \times log10(10^(L1 \div 10) + 10^(L2 \div 10))$

For example, combining 10 dB and 10 dB gives about 13.01 dB because the intensity doubles. A power ratio of 2 is about 3.01 dB.

Practical context

Use this for estimates in audio, acoustics, and electronics. For hearing and exposure decisions, rely on measured sound data and appropriate safety guidance. Related tools include the noise exposure calculator, sound level converter, and ohms law calculator.