There are only two things you will spend cash on your first three weeks at OCS, haircuts and the PX. Only the first three weeks matter because after that you can use any ATM you want to get more cash. There is an ATM at OCS, but it is up to your staff if they let you use it or not. Because of this, I recommend you bring more than the suggested $300 on the OCS website.
You will immediately spend between $216 and $244 at the large and small bag issue. Yes, $56 (or $84) will probably last your first 3 weeks of OCS, but do you really want to chance it? I suggest bringing $400. Bring $250 (of those $400) in large bills for the large and small bag issue.
Haircuts are once a week and cost $6.25, as of winter 2006. You will save yourself a headache if you bring 3 $5 bills, 3 singles, and 3 quarters. I advise you to keep these in a Ziploc and use them only for your first 3 haircuts. There is nothing like 50 candidates all trying to get change from their twenty-dollar bills the night before haircuts.
Keep the rest of your money (which after large and small bag issue and haircuts should be around $150) in your wallet. Your wallet will be secured in your wall or footlocker. The only other thing you should spend money on will be PX calls on haircut day. If you want extra skivvie shorts, an inspection belt, or extra white tape you can buy it there.
You will have extra cash but this is a good thing. You can help that candidate who only brought $300 and needs more cash. And you won’t need to hit an ATM first thing on liberty, you can go straight to the bar.