Position size calculator for day traders

How position size is calculated

1. 1
   Dollar risk

   Account size × risk percent. A $50,000 account risking 0.5% can lose $250 on the trade. Or enter a fixed dollar amount instead.

2. 2
   Risk per share

   The distance between entry and stop. Buying at $42.30 with a stop at $41.80 risks $0.50 a share.

3. 3
   Shares

   Dollar risk ÷ risk per share, rounded down: $250 ÷ $0.50 = 500 shares, a $21,150 position. With a target at $43.80 the trade makes $1.50 a share, 3R.

Questions traders ask

Why size from the stop instead of buying a fixed number of shares?

A fixed 1,000 shares risks $100 with a 10-cent stop and $1,000 with a one-dollar stop. Sizing from the stop makes every trade risk the same amount, so one wide stop can’t erase a week of small wins, and results measured in R compare fairly across setups.

How much of my account should I risk per trade?

That’s your call. Many day traders cap risk per trade at a small, fixed fraction of the account, and 1% or less is a figure often quoted. Whatever you choose, keeping it consistent is what makes your stats mean something.

Is the loss at the stop really the most I can lose?

No. A stop becomes a market order when it triggers, so fast markets, gaps, halts, and thin small caps can fill well past it. Commissions and fees come on top. Treat the loss at the stop as the plan, not a guarantee.

What about buying power and shorting?

The calculator doesn’t know your broker’s limits. A tight stop can size a position larger than your account, which needs margin, and a short needs shares available to borrow. Check both before placing the order.