How large should a position be for a single contract?
A common way to calculate position size is: Position notional value ≈ account balance × risk percentage per trade ÷ stop-loss distance. Risk per trade is the amount you lose if a trade hits its stop-loss, roughly equal to the position’s notional value × the percentage difference between the entry price and the stop-loss price.
Keep the risk per trade small enough that even after several consecutive losses, most of your account balance remains intact, so one or two mistakes won’t seriously damage your account.
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Just one person’s opinion—take it with a grain of salt; this isn’t advice.