If you practice holding the oil in your mouth and keep the oil still (Snigda Gandoosha) in areas of your mouth – start with about 5-7ml and build up – 10ml is ideal for this technique.
If you are swishing (Kavala Graha) you will need less oil. The swishing action will produce more saliva and you will gradually increase the contents of your mouth. Start with too much and you will be uncomfortable before you are finished. The amount of time you are oil pulling will also influence how much oil you need. Start small (5ml) and build up on each oil pulling session.