Fountain pen nibs

[Garno]

Nibs, ..........

That's the very first time I have started a chat by saying nibs.

I really like a fountain pen and hope to make a few this year, however I am slightly unsure how to identify a nib size. (OK make that I have no clue).
To me the only difference between a #5 and a #6 are the numbers (5 and 6)
How do I size a nib? and what is the difference between the sizes, does one make a thicker line than the other?
I found this on Phil's site but it does not really have what I am looking for Beaufort Ink - Undertanding Fountain Pen Nibs Choosing The Right One

Thanks everyone

 

[flexi]

It can be a big daunting but #5 are smaller than #6 which are smaller than #8 but bigger than #5s....
The size of the line can be F... fine M... medium or B... broad, before you get into italics which are just metric measures.
For simplicity an Omega or Levech nib is a #5 medium, if you wish to change it you'll need a #5 F or B (in a kit housing( if bought from Phil)) or if you go italic, Only worry about the bigger sizes if you go kitless or do the Big Gent fountain pens

 

[Geoff Kent]

A number 5 nib fits a feed that measures 5mm across.A number 6 fits a feed 6mm across.And so on.A number 5 nib will not fit a 6mm feed and so on.The feed is the plastic piece with very narrow channels that allow ink to flow around the nib.This in turn fits into the plastic housing.Then the nib,feed and housing fit into the fountain pen section.
If you are still unsure reread Phils piece,it explains everything very clearly.