Gross profit (GP), net profit (NP) and profit before interest and tax (PBIT) are all well-known descriptors, but I often find that many people are confused about what each of these terms mean. It's really important that you, as a marketeer, knows how to calculate your GP accurately. You should also be aware of all of your overheads that are deducted to arrive at NP too.
In addition to business GP, NP and PBIT you should also know your profit margins by product, range and grouping. Without this you will be completely in the dark when it comes to setting your prices and profit margins. Vital if you are thinking about introducing a discount, rebate or commission structure.
Above all, being clear about the different profit margins by product will help you to determine whether or not you are selling a 'premium' or a 'loss-leader' product. You should only have one or two loss-leader products in your range; otherwise you'll never make a profit! Balancing this with premium priced products is a good test. You should always have more premium priced products than loss leaders. Above all, be clear which products are the so-called 'loss-leaders'.
Other issues that will affect your profit are: