Position Sizing
Position sizing is deciding how much to buy so that a hit stop-loss costs a fixed share of your account.
Position size follows from the risk, not from conviction: multiply the account by the percentage you accept losing on one trade, then divide by the distance from entry to stop. A $10,000 account risking 1% with a stop 5% below entry buys a $2,000 position.
Because the stop distance changes with every setup, the position size changes too: a wide stop means a smaller position, a tight stop a larger one. The position size calculator does the arithmetic, including whether the result needs leverage.