Free Trading Tool
Position Size Calculator
Enter your account capital, risk per trade, entry price, and stop loss to get your position size in units — and, for futures and options, the number of whole lots that fits inside your risk budget. No signup required.
Exchanges revise F&O lot sizes periodically — check the current contract specification and use Custom lot size if it differs from the preset.
Your Result
Position Size (units)
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Number of Lots
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Rounded down to whole lots so you stay inside your risk budget.
Risk Amount
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Risk Per Unit
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Actual Risk at Whole Lots
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Position Value
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Always paper trade first. This calculator is an analytical tool to help you size a trade before you risk capital — it is not investment advice and does not guarantee results. Test any strategy on a paper account before trading it live.
Want the full definition, sizing methods, and common mistakes? Read the position sizing definition →
Why Position Sizing Matters
Position sizing is the only input in a trading plan that you control completely. You cannot control whether a setup works, but you can control exactly how much the account loses when it doesn't. That makes sizing the single largest lever over drawdown — and drawdown, not win rate, is what ends most trading accounts.
The practical consequence is that a strategy with a genuine edge can still fail if it is sized badly. Losing streaks are a normal statistical feature of any edge; the strategy only pays out if the account is still alive when the winning period arrives. Sizing every trade to a fixed small fraction of equity is what guarantees that survival: the position shrinks automatically as the account draws down, and grows again as it recovers.
It also removes the most common source of inconsistency. Two trades with the same "10 lots" label can carry wildly different risk if one has a 20-point stop and the other a 200-point stop. Sizing from the stop distance — as the calculator above does — makes every trade risk the same amount, which is the only way a win rate or expectancy figure means anything.
| Risk Per Trade | Profile |
|---|---|
| 0.25% – 0.5% | Conservative — suited to high-drawdown strategies |
| 0.5% – 1.0% | Standard — used by most professional systematic traders |
| 1.0% – 2.0% | Aggressive — only with a high win rate and strong R:R |
| Above 2.0% | Drawdowns become severe and hard to recover from |
The Position Size Formula
The fixed-fractional method runs in three steps, and the calculator above simply automates them:
Risk Amount = Account Capital × (Risk % ÷ 100)
Risk Per Unit = |Entry Price − Stop-Loss Price|
Position Size = Risk Amount ÷ Risk Per Unit
Number of Lots = floor(Position Size ÷ Lot Size)The last line is where most Indian F&O traders go wrong. Futures and options trade in fixed contract lots, so the ideal unit quantity almost never divides cleanly. Rounding up to the next lot pushes you past the risk budget you just calculated — sometimes by 30-40% on a small account. Always round down, and treat the leftover as unused risk capacity rather than a reason to take one more lot.
Worked example — a NIFTY options trade
(Illustrative figures for teaching the calculation, not real market data.) A trader has a ₹5,00,000 account and risks 1% per trade. They plan to sell a NIFTY option at a premium of 180 and will exit if the premium reaches 150 — a 30-point adverse move per unit. NIFTY's lot size is 65.
- Risk Amount = ₹5,00,000 × 1% = ₹5,000
- Risk Per Unit = |180 − 150| = 30
- Position Size = ₹5,000 ÷ 30 = 166.67 units
- Number of Lots = floor(166.67 ÷ 65) = 2 lots (130 units)
- Actual risk at 2 lots = 130 × 30 = ₹3,900 — comfortably inside the ₹5,000 budget
Note what rounding up would have done: 3 lots is 195 units, which risks ₹5,850 — 17% more than the plan allowed, on a decision that felt like a rounding detail. Note also the second output the calculator gives you, actual risk at whole lots. That is the number to record in your trade journal, not the theoretical risk amount, because it is what the account will genuinely lose if the stop is hit.
Common Position Sizing Mistakes
- Trading a fixed lot count regardless of stop distance. "I always trade 2 lots" is not a risk rule — it is a habit. The same 2 lots risks ₹2,600 on a 20-point stop and ₹13,000 on a 100-point stop. Size from the stop, every time.
- Rounding lots up to avoid "wasting" risk budget. Unused risk capacity costs nothing. Exceeding your risk budget compounds across a losing streak into exactly the drawdown the sizing rule existed to prevent.
- Widening the stop to make a bigger position fit. This is the same error in reverse: the stop level is set by where the setup is invalidated, not by the size you wanted to trade. Moving it to justify a position destroys the risk calculation and the R:R together.
- Sizing up after a winning streak. Increasing size after several wins puts maximum capital at risk precisely when results are statistically most likely to revert to the strategy's average. Let the fixed percentage scale the position, not your confidence.
- Sizing against starting capital instead of current equity. Fixed-fractional sizing only protects you if the percentage is applied to today's account value. Sizing off the original deposit after a 20% drawdown means you are quietly risking 1.25% per trade while believing you are risking 1%.
- Ignoring correlation across open positions. Three positions each risking 1% in the same index or sector are effectively one 3% position. Size against total portfolio risk, not per ticket.
How Quantzee Helps
Every position sizing calculation depends on one number: a stop level you can define before you enter. Quantzee's indicators (see the AI Adaptive Quant Toolkit and SuperTrend Pro+) plot the invalidation level alongside the entry signal, which gives you the stop distance this calculator needs at the moment of entry rather than after the fact. Because the signals are non-repainting, that stop distance does not shift retroactively on the historical bar — so the size you calculated is the size the setup genuinely offered.
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