if you want to calculate your risk of ruin, it's not enough to have just your edge (house's edge actually). you also need the deviation of that edge. for a game like blackjack I guess the most simple thing would be to find this info somewhere online if it exists. if you can't find it for that exact variant I guess you would just need to take an approximation, it would help if you know if your variant is more or less in house's favor than the "basic". if you want exact numbers, you'd need to solve that variant yourself...
I don't know if there's an exact formula for risk of ruin, but it could be easily simulated. if you know some basic programming, you can do it yourself.
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House edge of 4.724%. The charts online list a standard deviation of 2.724
is standard deviation that small in blackjack? in poker std. dev. is like 15x bigger than edge (winrate).