There is a rough guide that says they need 2-2.5oz per lb of body weight in 24 hours, but that is a very rough guide.
At 2 months my two were taking about 4oz every 3 hours during the day and we tried the DF (hit and miss) and 1 or sometimes 2 nightfeeds.
How much is your LO taking now? You need to be guided by them really. When you bottle feed you should have enough in the bottle so that there is a bit left at the end of a feed. You know then that they have stopped because they are full (as a breastfed baby would) and not just because the bottle is empty. If they are draining the majority of bottles during the day you need to add another oz.
HTH!
Laura