Originally Posted by Welsh-lad:
“You can buy a plastic thingy with different size round holes in.

Say you choose the '1 portion' hole, you put the spaghetti in and if it doesn't fit there's too much, take put out a few strands, and try again.
Here's an example:

http://www.hartsofstur.com/acatalog/...FYYBwwodTXkAkw

Nurses can get those in cardboard.
They're used for gauging appendages when fitting catheters.