Position Size Calculator
Calculate exactly how many shares or units to trade based on your account size, risk tolerance, and stop-loss distance.
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Most disciplined traders risk 0.5–2% of their account per trade.
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Works whether you're going long (stop below entry) or short (stop above entry).
Results
Position size—
Amount at risk—
Risk per unit—
Position value—
Share of account deployed—
Account remainder—
Amount at risk—
What a position size calculator actually tells you
Most trading losses don't come from picking bad trades — they come from betting too much on any single one. A position size calculator flips the usual order of decisions: instead of picking how many shares to buy and hoping the loss stays small, you decide upfront how much money you're willing to lose on the trade, then work backward to the exact number of shares or units that guarantees the loss stays at that level if your stop-loss is hit.
It answers one specific question — how many units should I trade? — and deliberately leaves the question of whether to take the trade at all to you.
The formula
Position size = (Account size × Risk %) / |Entry price − Stop-loss price|
- Account size — your total trading capital
- Risk % — the share of your account you're willing to lose on this one trade
- Entry price − Stop-loss price — your risk per unit, which works the same whether you're going long (stop below entry) or short (stop above entry), since the calculator uses the distance between them either way
A worked example
Account size ₹5,00,000, risking 1% per trade, entry at ₹250, stop-loss at ₹235. That's ₹5,000 you're willing to lose (1% of ₹5,00,000), and ₹15 of risk per share (the gap between entry and stop). ₹5,000 ÷ ₹15 works out to 333 shares.
If the stop-loss is hit, you lose close to ₹5,000 — not because you got lucky, but because the position was sized to guarantee it. If the trade works instead, your gain is whatever multiple of that ₹15-per-share risk your target represents; a 2:1 reward, for instance, would be a ₹30 gain per share on the same 333 shares.
Choosing a risk percentage
0.5% to 2% per trade is the range most professional and disciplined retail traders work within. The exact number matters less than staying consistent — the real value of risk-based sizing is that a string of losing trades, which happens to every strategy sooner or later, costs you a predictable, survivable slice of your account instead of an unpredictable one. Risking 5% or 10% per trade might feel fine while you're winning, but a handful of losses in a row at that size can do damage that takes far longer to recover from than it took to create.
Newer traders are generally better off nearer the low end of that range. There's no cost to sizing conservatively while you're still finding out whether a strategy actually works.
What this calculator does not account for
- Lot sizes. Futures and options trade in fixed lot sizes, not arbitrary unit counts. Round to the nearest tradable lot, which may mean your actual risk differs slightly from your target.
- Brokerage, slippage, and taxes. These add to your real cost and will make an actual stopped-out loss somewhat larger than the raw price-risk figure shown here.
- Correlated positions. If you hold five long positions that tend to move together, your real portfolio risk is higher than five times your per-trade risk — this tool sizes one trade at a time, not a whole portfolio.
- Where your stop-loss should go. This calculator assumes you've already decided your stop price. It doesn't tell you where that should be — that's a separate decision based on chart structure, volatility, or your own strategy.
Treat the output as the ceiling your risk tolerance allows, not a target you're obligated to fill.
Frequently asked questions
What percentage of my account should I risk per trade?
Most disciplined traders risk between 0.5% and 2% of their account on any single trade. Risking more than that means a short losing streak, which is normal even for a good strategy, can do serious damage to your capital. Beginners are usually better off starting near the low end of that range.
What if the position size comes out as a fraction?
Round down to the nearest whole share, lot, or contract if your market does not support fractional trading. Rounding down keeps your actual risk at or below your target; rounding up would let it exceed what you intended to risk.
Does this calculator account for brokerage, slippage, or taxes?
No. It calculates raw position size from price risk only. Brokerage, slippage, and taxes all add to your effective cost and will make your real-world loss on a stopped-out trade slightly larger than the figure shown here.
How is this different from a margin calculator?
A margin calculator tells you how much capital you need to open a leveraged position. This calculator tells you how many shares or units to trade so that if your stop-loss is hit, you lose only the amount you chose to risk. They answer different questions and are often used together.
Should I risk the same percentage on every trade?
Many experienced traders vary risk slightly with conviction, but keeping it consistent is the safer habit for most people, especially early on. Varying risk by feel often means risking the most on trades you are most excited about, which are not reliably the ones most likely to work.
What if the calculated position size is more than I can afford?
Then your stop-loss is too far from your entry for your account size at your chosen risk percentage. Either move your stop closer, reduce your risk percentage, or skip the trade. The position size this tool gives you is a ceiling based on risk, not a target to force your capital to match.