Free tool
Position size calculator
Decide the risk first, in money. This answers how many shares, units or contracts that risk buys, and it always rounds down, so you never risk more than you meant to.
Add account size, or switch the risk to a fixed amount.
Why size from risk
Most blown accounts die in one to three oversized trades, not in a hundred small ones. Picking the share count first and finding out the risk later is how that happens. Working the other way, risk first, size second, keeps any single wrong trade survivable.
The math, in the open
Risk budget is your account times the percent you chose. Risk per share is the distance from entry to stop. Size is the budget divided by that distance, rounded down to a whole share. For options and futures, you give the max loss per contract and the same division applies. On a forex pair the risk lives in the quote currency, and the result says so instead of converting with a rate it does not have.
What a calculator cannot see
It sizes the next trade. It has no idea what you did on the last twenty. Travise reads every trade you log against your own record, scores the decision rather than the outcome, and turns the worst habit it finds into a rule it checks on every trade after.