[Wylecoyo]

Welcome aboard! Just a quick guess, but I would think if you had enough chips to cover 1/3 to half of your field for rebuys you would probably never be short. Even better would be to simply use higher value chips for rebuys - for example if you are doing a T5000 tournament with 25/100/500/1000 chips handed out at the beginning of play you could simply give rebuys 5 1000 chips or 1 5000 chip and let them get change from other players. This would maximize your rebuy potential while minimizing the number of extra chips you need to buy or keep track of.

As far as add-ons go, I would always ensure you can cover one for every player in the game because if one person adds on many more may follow suit. You could cover add-ons with higher value chips as well if you wanted to.

In short, if you are running a 10 player game, maybe get enough starting chips to cover say 12 players and then enough higher value chips to allow for coloring up the entire field of play. This way you can use the coloring up chips for rebuys and add-ons and still have the higher value chips in play to make up the slop.

I sure hope this makes sense and does not come across as a crazy ramble.