#screwblr

First off, notation. It's standard to note diameter then thread spacing separated by a hyphen, like this: Dia. - Thread

Thread spacing (or pitch if you're fancy) is measured by threads per inch of length down the screw. You can count them by hand, or take a screw/nut of the same diameter and a known pitch and try to get them to mesh together. If it fits, they have the same pitch.

Then there's the type of screw, and there are many resources you can use that are reliable and just one search away, and while they can contradict one another, just pick what makes sense.

There's a weird system that was once used for wire gauges whose name escapes me, but for some reason it is used for screws to, even to this day. It is denoted by the # and a number after it. If you want to translate this to something usable you have to look up a table and stuff and it's a whole deal and I couldn't tell you for the life of me why it's still used.

Finally, the length of screws comes after the diameter and pitch notation like such: Dia. - Pit. X Len.

Here's the list (length not included):

5/16" - 18

1/4" - 20

3/8" - 16

#10 - 32

#10 - 24

#8 - 32

1/2" - 13