Position Sizing

Right now we do have risk per trade.
The max we can risk on any given trade. Ideally market does not care what I want to risk.
There should be an option for me to put a stop loss based on the pivot point or wherever on the chart and entry price.
Based on the range the number of contracts I can take will be caluclated.

Ex: if my entry is on 100 and I place my stop loss at 98 and I want to risk $100 per trade then I can take 50 shares(I know we do only futures, just for an example).
2nd example if my entry is 100 and my stop loss is not until 95 based on the chart then I can take only 20 instead of 50 in the above example.
This will make a huge difference.