I believe setting stop-losses is just one side of the story. After determining your stop-loss, a pro trader should define how much loss he's willing to take. For example, I only want to lose $100 per open position out of my $10,000 capital. The size of the position should result in a $100 loss once stop loss is triggered.
What you just say is definitely part of the percentage based stop loss strategy, It is called VAR or the Value at risk. Why we should use it? In order for us to know how much capital are we going to put in a trade and also to know how much risks are we going to take. The ideal risk in every trade is 1%. The formula to get the bar is you going to divide the percentage stop loss that you prefer to your 1% capital. For example if you have $100,000 as a capital and your plan is to have cut loss whenever the price reached -3%. You will basically get the 1% of the 100,000 which is 1,000 then you are going to divide the 3% to $1000 because it is the 1% of $100,000 then you will get an answer of $33,333. Which means that you can only put maximum of $33,333 in one trader if you plan to have stop loss which is at -3%