This is a simple calculation. You enter the value of your sales and the amount of the gross cost of sales and the calculator provides you with the amount of the gross profit and the profit margin as a percentage of your sales.
For example, if you sell £10,000 of your product of service and it costs you £3,000 (excluding overheads) to produce that level of sales, your gross profit (before overheads and other costs) will be £7,000 and your gross profit margin will be 70% of your sales turnover.
This reverses the gross profit margin calculator. You enter the amount of gross profit margin (profit before overheads and other indirect costs) you intend to build into your sales price. You then enter the level of sales you are making and the calculator with tell you the amount of your cost of sales (i.e. your direct costs excluding overheads etc) and the amount of your gross profit.
For example, if your gross profit margin is 22% and your sales are £12,500, your cost of sales will be £9,750 and your gross profit will be £2,750.