* 3 db = x 2
* 10 db = x 10
These are enough (the article mentions more but they are not needed since you should be able to create all db values from these).
Now, when you've got a db value, try to write it as the sum or difference of these values. For example,
* 1 db = 10 db - 3 * 3 db
* 7 db = 10 db - 3 db
* 12 db = 3 db * 4
* 17 db = 2 * 10 db - 3 db
Now, you can convert these to absolute values using multiplication and division
* 1 db = 10 db - 3 db - 3 db - 3db = 10 / 2 / 2 / 2 = 1.25
* 7 db = 10 db - 3 db = 10 / 2 = 5
* 12 db = 3 db + 3 db + 3 db + 3 db = 2 * 2 * 2 * 2 = 16
* 17 db = 10 db + 10 db - 3 db = 10 * 10 / 2 = 50
* 36 db = 10 db + 10 db + 10 db + 3 db + 3 db = 10 * 10 * 10 * 2 * 2 = 4 000
The same algorithm of course can be used to convert from absolute numbers to decibels:
2000 = 2 * 10 * 10 * 10 = 3 + 10 + 10 + 10 = 33 db
Notice these all are approximations however these are really good approximations and more than enough to very quickly understand what a gain of 50 db means!