yourfinance Options-income decision control room

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Position-size calculator

This is the same sizing logic that runs inside yourfinance, ported to this page. It answers the question that comes before every trade: given the account and where the stop sits, how large can this position be — and which limit is actually binding, the risk budget or the concentration cap?

Nothing you type here leaves your browser. The arithmetic runs in JavaScript on your own machine. The calculator itself has:
  • no server call, no fetch and no tracking pixel;
  • no cookies and no localStorage write — close the tab and the numbers are gone;
  • no fonts or images loaded from anyone else's domain.

Turn off your network connection and the calculator still works. The one script from elsewhere is Cloudflare Web Analytics, which our host adds to every page of this site: it counts the page view and measures load time, without cookies, and what you type is not part of it.

Used by both tools below. Currency-agnostic — enter it in whatever currency your account is denominated in.

Size from your stop

Fixed-fractional sizing with a concentration cap.

The most you accept losing if the stop is hit.
Defaults to 20%. A single name at more than a fifth of the account stops being a position and starts being the portfolio.

Size from your track record

Half-Kelly, hard-capped. Requires an honest sample.

A decimal strictly between 0 and 1. 0.55 means 55% of closed trades were winners.
Enter as a positive number.
Defaults to 0.25. Edge estimates from small samples are unreliable, so the cap exists for a reason.

Fixed-fractional sizing truncates to whole shares — it never rounds a position up past your risk budget. The Kelly panel reports half-Kelly by default because full Kelly assumes you know your edge exactly; nobody does. Neither tool knows anything about the instrument you are trading, and neither one can make a negative-expectancy strategy profitable.