If you'd like to make 20% gross profit, you need to mark up by 25%. So just multiply your costs by 1.25. Of course you need to ensure you have enough in that 20% gross profit to cover overheads and other costs which are not direct costs of sales. And consider if the market can bear higher pricing. Or carry on as you are with your 20% mark up/16.6% gross profit if you're happy with that. Disclaimers: I don't have a maths degree. I am not an accountant.