Position Size Calculator
Position Size Calculator
Account & Risk
Trade Setup
Direction is detected automatically: a stop below entry is a long trade, above entry is a short.
Based on your results — what to do next:
Model the full trade outcome
Sized at 100 units ($5,000), see profit after fees if the target of $57.50 is reached.
See what consistent returns compound into
Risking 1% ($250) per trade on a $25,000 account — project what a steady annual return does over a decade.
Keep trading capital in context
Your $25,000 trading account should be a slice of the whole picture. Track it against assets and debts.
A position size calculator tells you how many shares, contracts, or coins to buy so that hitting your stop-loss costs only a fixed percentage of your account. It divides your dollar risk by the distance between entry and stop, then reports the resulting position value, leverage, reward-to-risk ratio, and break-even win rate.
How the Position Size Calculator Works
① Dollar risk
Risk $ = Account × Risk%
The most you are willing to lose if the stop is hit.
② Position size
Units = (Risk $ − Round-trip commission) ÷ |Entry − Stop|
Rounded down to whole units if you choose.
③ Reward-to-risk and break-even win rate
R = |Target − Entry| ÷ |Entry − Stop|; Break-even win rate = 1 ÷ (1 + R)
Ignores slippage and spreads.
| Variable | Meaning | Typical Value |
|---|---|---|
| Account | Trading capital | Any amount |
| Risk% | Share of account lost if stopped out | 0.5–2% |
| Entry / Stop | Planned entry and exit-on-loss prices | Chart-based |
| R | Reward-to-risk ratio | 2:1 or better |
Worked Example — $25,000 account, 1% risk, buy at $50 with a stop at $47.50 and a target of $57.50
- Risk budget: $25,000 × 1% = $250
- Risk per share: $50 − $47.50 = $2.50
- Position size: $250 ÷ $2.50 = 100 shares ($5,000, 20% of the account)
- Reward: 100 × $7.50 = $750 → reward-to-risk 3 : 1
- Break-even win rate: 1 ÷ (1 + 3) = 25%
💡 Pro-Tip
Size from the stop, never from the dollar amount you want to invest. A tight stop lets you hold a larger position for the same risk, but only if the stop sits at a level that makes sense on the chart. Placing a stop too close just to inflate size usually gets you stopped out by normal noise. Pick the stop first, then let the calculator tell you how much you can afford to buy.
Position Size Calculator FAQ
How do you calculate position size?
Position size = (account size × risk %) ÷ (entry price − stop-loss price). With a $25,000 account, 1% risk, entry $50 and stop $47.50, you risk $250 at $2.50 per share, so you buy 100 shares.
How much of my account should I risk per trade?
Many traders risk 0.5% to 2% of their account per trade. At 1%, a string of 10 consecutive losses costs about 9.6% of the account; at 5% it costs about 40%.
What is a good reward-to-risk ratio?
Many traders look for at least 2:1. The break-even win rate is 1 ÷ (1 + R), so a 3:1 setup only needs to win 25% of the time, while a 1:1 setup needs 50% before costs.
Does position size change for short trades?
The math is the same, using the absolute distance between entry and stop. The stop sits above entry for a short and below entry for a long.