If you are like me, converting numbers into dB values has not come easy. Well, I recently attended a training class offered by my employer that, as part of the up front refresher material, provided the best method I have ever seen for quickly calculating the correct answer (next to using a calculator of course).

Step 1:

The first step requires a little memorization. You will need to memorize all the dB values for the numbers 1 through 10. Here is a good estimation for each value:

1 = 0 dB
2 = 3 dB
3 = 5 dB
4 = 6 dB
5 = 7 dB
6 = 8 dB
7 = 8.5 dB
8 = 9 dB
9 = 9.5 dB
10 = 10 dB

While these aren’t exact numbers, they are close enough for quick, off the cuff, calculations. Also, we are ignoring fractional values because this method is meant for quick estimates, not exact calculations.

Step 2:

The next step is the actual conversion. For a number that is N digits long, the dB value will be 10 x (N-1) plus the dB value of the Nth digit (furthest to the left).

For example, convert 7,6453,785,473 to dB.

This value is 11 digits long, so the estimated dB value is (10 x 10) + 8.5) or 108.5 dB.

Plugging that number into a calculator yields a value of 108.8 dB for an error of 0.3 dB.

It works for any number. Of course, the larger the number, the higher the margin of error will be.

Let’s try it one more time:

Convert 584,369,854,587,523,698,452,566

This value is 24 digits long, so the estimated dB value is (23 x 10) + 7) or 237 dB.
The calculator value is 237.6 dB

Hope this helps.