There are lot size / lot risk calculators, available in the Market for that kind of thing.
That acctualy depends from few variables but in short most important is :
a) your broker margin call level
b) pip value
c) lot size
So just for this calculation purpose lets assume that you get margincall when your equity reach 10% of balance.
This means that equity amount that you can use is 180 usd.
Now all you need to do is divide your equity by number of pips / value.
To simplify lets assume that you trade EURUSD and your base currency is USD so 1 pip has a value of 10$ with 1 full lot size.
You wrote that you trade 0.04 lots, so your 1 pip will have a value of 0.4$. This means that to get stop out you will need 450 pips move.
(180 usd avaliable equity / 0.4$ pip value per lot = 450 pips). I made this calculation using PIP value so 0.0001, if you want to
calcualte this using tick which is 0.00001 then just add one 0 at the end. (you will have 4500 ticks which is 450 pips)