Gambler's Ruin Calculator

Calculate the probability of reaching a target before going broke.

Gambler\

Fill in the fields below to calculate

Starting Capital (k)

Target Capital (N)

Win Probability p (0-1)

Enter your values above and tap Calculate to see the result.

Probability of Reaching N

Ruin Probability

Formula

If p≠0.5:
P = (1-(q/p)^k)/(1-(q/p)^N)
If p=0.5: P=k/N

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Pro Tips

Results update as you type — change any field to see the effect immediately.

Check that every value uses the same unit before comparing results.

Use the copy button to paste the gambler's ruin figures into a note or spreadsheet.

Nothing is sent to a server, so you can use this with private figures.