Lot size ,StopLoss and Risk Amount

Hello people, I don’t know how to calculate the correct lotsize for Gold spot, brent,btcusd, palladium, platinum, DAX 30 and DJ30.
Lets say I have a riskAmount of $100. How do I calculate the correct lotsize that will give $100 if price move against me.
For other currency pairs, if am risking $100 and I have a stoploss of 550 pips, I know my Lotsize will be 0.18. When I tried it with all the above instruments, the calculation seems wrong. Anyone to help me out please. Thank you already.

Hm. There is something wrong with your post: 550 pips with 0.18 lots are not equal to $100. That should be 55 pips. You can use the baby pips position size calculator for you forex trading or other tools which have also precious metals (there is one on myfxbook). For BTC, DAX and DOW you have $1 per point (13001.00) per 1 lot, so if you want to stay with your 55 pips and $100 risk you would need a lot size of 100 / 55 = around 1.80
Or you can simply use some Expert Advisor, which will calculate the lot size for you when you enter your risk (Mini Terminal in MT4/5 has this option for example).
I hope this was helpful.