Risk of ruin sounds dramatic. Your sample is small.
The textbook formula assumes a trader you are not. Here is what it can still tell you.
Risk of ruin asks a simple question: if you keep betting the same way, how often does the account reach zero?
The maths is clean. The assumptions are heroic. Fixed win rate, fixed payoff, fixed bet size, no deposits, no tilt, no lot-size changes, no market regime shift. Your book breaks most of those before lunch.
What the formula actually eats
It wants a win rate, an average win, an average loss, and a fraction of capital risked per trade. All four come out of your closed history, so all four change the moment you move the date filter.
Run it if you enjoy spreadsheets. Just print the trade count next to the result in the same font size.
Win rate measured on the same strategy over different windows. Small samples swing wildly. Illustrative journal data, not a live book and not a performance claim.
Small samples flatter everyone
Forty trades can produce a win rate that vanishes at two hundred. Any ruin figure built on forty trades is a coin wearing a lab coat.
A practical rule for a personal journal: hide the fancy statistic until the sample crosses a threshold you set for yourself, and show the trade count instead.
What it is good for
Two things. First, a reality check on bet fraction: if the historic sample says you risked 12% of capital per idea, the model will be brutally clear about that path. Second, an argument for smaller, boring size when you cannot explain last month.
What it is not: an allocation decision made by software, or a forecast of the next two hundred fills.
Key takeaways
- Ruin maths describes a sample, it does not forecast one.
- Always print n beside the number.
- Deposits, withdrawals and changing size break the textbook model.
Not advice, not a call. NiyataBook is a personal trading journal, not a SEBI-registered investment adviser or research analyst. Everything above looks backwards at trades that already closed. What happened in a book does not promise what happens next, and F&O can take a year’s savings in a week.