Calculate the dB value from power ratio or the power ratio from dB value.
Remember to press the ENTER key after you type in a value.
dB, or Decibels always refer to the ratio between two numbers. For example, when one signal is 3dB stronger than another signal, that means that one signal is twice as powerful as another signal. The ratio of the power level of the stronger signal to that of the weaker signal is 2 to 1.
Found this calculator at http://www.bessernet.com/jobAids/dBCalc/dBCalc.html.