Haven't been here a while, so this might not be new news.

http://www.twonix.com/index.jsp?action=ruin

Found this free download for a Longest Lossing Streak calculator based on mathematical probabilities (strike rates etc) which you put in. There used to be a good site that did this but it no longer operates.

Hope this post is useful for some people who like me, want to know more about the odds of success.

the way i calculate a loseing streak is i look at my bank balance and if i have $10 i know the loseing streak has to end soon because i am broke and can't bet anymore

This is the formula I use. It might look a bit complicated but once you've used it a few times it's pretty easy.

Predicting the number of losing runs of a given length, against a given strike rate:

X = N x S^2 x (1 - S)^L,

where
X = number of losing runs of length L
N = number of results
S = strike rate
^ = to the power of
L = length of losing run you wish to investigate.

nb. S is in decimal format eg. s/r of 75% would be 0.75

I find if you make N 10,000 it's pretty accurate.