Most account blow-ups come not from bad entries but from oversized positions. This calculator inverts the usual workflow: instead of guessing how many coins to buy, you declare how much you are willing to lose, and it tells you the exact position that respects that limit given your stop-loss.
How it works
The fixed-fractional method starts from your dollar risk — account balance times the risk percentage. The distance between entry and stop-loss is your risk per coin, so the quantity that loses exactly your dollar risk at the stop is dollar risk divided by risk per coin. Multiplying that quantity by the entry price gives the position value, and comparing it to your balance reveals the implied leverage; anything above one means the position is larger than your cash.
Optionally, the tool computes the Kelly Criterion from your historical win rate and your reward-to-risk ratio. Kelly is the account fraction that maximises long-run growth, and it also shows half-Kelly, the more conservative figure most professionals actually use. A zero or negative Kelly flags a trade with no positive expectancy.
Example and notes
On a 10,000-dollar account risking 1 percent, with entry at 100 and stop at 90, the risk per coin is 10 dollars and the dollar risk is 100, so the position is 10 coins worth 1,000 dollars — comfortably within balance. Tighten the stop and the quantity grows, eventually demanding leverage. Use fixed-fractional sizing for survival and Kelly as a sanity check on aggressiveness; the two answer different questions and are best compared, not merged.