Confusion often stems from the simplest of calculations: dose of fish oil.
Actually, you and I don't take fish oil for fish oil. We take fish oil for its content of omega-3 fatty acids, the dominant ones being EPA and DHA. The contents of fish oil outside of its EPA + DHA content likely exert little or no benefit (beyond that of other dietary oils).
To determine what you are currently taking, simply examine the back of your fish oil bottle and look for the EPA + DHA composition. This should be clearly and prominently labeled. If not, don't buy that brand again. Add up the EPA + DHA content per capsule, then multiply by the number of capsules you take per day. That yields your daily EPA + DHA intake.
The only other substantial source of omega-3 fatty acids is fish. Other food sources, such as non-fish meats, eggs, etc., contribute little or none. Processed foods that bear health claims of "contains heart healthy omega-3" often contain linolenic acid or flaxseed oil, which contributes very little to total EPA + DHA, or contain relatively trivial quantities of DHA. What are you doing eating processed foods, anyway?
What should the total daily dose of EPA + DHA dose be? That depends on what your goals are.
If your goal is to modestly reduce the risk of dying from heart attack, then just eating fish a couple of times per month will begin to exert an effect, or just taking a dose of 300 mg EPA + DHA per day from a low-potency capsule will do it. However, that's an awfully unambitious goal.
Our starting omega-3 dose in the Track Your Plaque program has, over the years, increased and now stands at 1800 mg EPA + DHA per day. However, the dose for 1) full reduction of triglycerides and/or triglyceride-containing abnormal lipoproteins, 2) reduction of Lp(a), and 3) the ideal dose for coronary and carotid plaque control are substantially higher.
But once you know your desired daily target of total EPA + DHA, you can easily determine the quantity of capsules to take by doing the above arithemetic, totaling the EPA + DHA per capsule. For example, if you have been instructed to take 6000 mg per day EPA + DHA, and your capsule contains 750 mg EPA + DHA, then you will need to take 8 capsules per day (6000/750).