Pick two very large numbers, one much smaller than the other. For this example, pick 1 billion for the large number and then pick 10 for the small number.
Calculate the ratio of the big number to the small number. Divide the larger number by the smaller number. For this example, divide 1 billion by 10. Enter in your calculator 1,000,000,000, press the divide symbol then enter in 10. Examine the result displayed on your calculator. Check to see if the number displayed is 100 million, which is a 1 followed by 8 zeros.
Calculate the logarithm of the ratio obtained in the previous step. Locate the logarithm button on your scientific calculator. Press it. Now enter in the ratio obtained in the previous step, 100,000,000. Examine the result on the calculator’s display. Check to see if it reads 8. Conclude that 8 is the logarithm of 100,000,000.
Calculate the dB Gain. Multiply the logarithm of the ratio obtained in the previous step by 10. For this example, since the logarithm was 8, the result is 80, since 8 times 10 is 80. Conclude that the dB gain is 80.