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Work out the exact quantity to trade from your capital, risk limit and stop-loss — with F&O lot rounding for NSE contracts.
Max Risk (1R)
₹5,000
1% of capital
Stop Distance
100.00
points / per unit
Position Size
50.0
units / shares
Position Value
₹11.25 L
notional
For educational purposes only. Not financial advice. Verify calculations before trading.
Position Size = Risk Amount ÷ (Entry Price − Stop Price)
where Risk Amount = Capital × Risk %
Both halves matter. The numerator is the rupee figure you accept losing. The denominator is what one share or unit costs you when the stop is hit. Position size is simply the quantity that makes those two numbers agree — which is why the stop-loss has to be chosen before the size, never after.
Capital ₹5,00,000, risking 1% (₹5,000). You buy a stock at ₹850 with a stop at ₹820, so each share risks ₹30. Position size = ₹5,000 ÷ ₹30 = 166 shares, costing ₹1,41,100. Note the position is worth 28% of the account while risking only 1% of it — position value and risk are different things, and confusing them is what makes traders think they are being conservative when they are not.
Capital ₹5,00,000, risking 1% (₹5,000). You buy a Nifty call at ₹180 with a stop at ₹140, risking ₹40 per unit. Ideal quantity = ₹5,000 ÷ ₹40 = 125 units. At the current Nifty lot size of 65 that is 1.92 lots — so you trade 1 lot, not 2. One lot risks ₹2,600 (0.52% of capital); two lots would risk ₹5,200, past the limit you just set. Always round down, and check the current lot size first — NSE revises them and Nifty moved from 75 to 65 in January 2026.
Account $10,000, risking 1% ($100). Long EUR/USD at 1.0850 with a stop at 1.0800 — a 50-pip stop. On a standard lot each pip is roughly $10, so 50 pips risks $500 per lot. Position size = $100 ÷ $500 = 0.2 lots, which is two mini lots.
The 1–2% convention is arithmetic, not folklore. Losing streaks are unavoidable at any win rate, and what decides whether one ends your account is the size of each individual loss.
| Risk per trade | Account after 10 straight losses | Gain needed to recover |
|---|---|---|
| 1% | 90.4% | 10.6% |
| 2% | 81.7% | 22.4% |
| 5% | 59.9% | 67.0% |
| 10% | 34.9% | 186.8% |
A ten-loss streak is ordinary at a 50% win rate. At 1% risk it is an inconvenience; at 10% risk the account needs to nearly triple to get back to where it started. Losses and recoveries are not symmetrical, and that asymmetry is the entire argument for small position sizes.
Indian derivatives add two constraints that generic calculators ignore. First, contracts trade in fixed lots, so the ideal quantity almost never lands on a whole number and must be rounded down. Second, round-trip charges — STT, exchange transaction charges, stamp duty, SEBI turnover fees and GST — are real money on every exit. A stop that reads as a 1% loss frequently settles nearer 1.2% once those are paid, so sizing marginally under your limit is prudent rather than timid.
Expiry day deserves a separate rule. Premiums decay fast and spreads widen, so the price you exit at can differ materially from the stop you set. Many traders halve position size on expiry for exactly this reason.
Position size = (Capital × Risk %) ÷ (Entry price − Stop-loss price). The numerator is the rupee amount you are willing to lose; the denominator is how much you lose per share or unit if the stop is hit. Dividing one by the other gives the quantity that makes those two numbers agree.
Most professional traders risk 0.5% to 2% of capital per trade. The reason is mathematical, not superstitious: at 2% risk a 10-trade losing streak costs about 18% of the account, which is recoverable. At 10% risk the same streak costs 65%, which needs a 186% gain to recover from.
F&O positions are sized in lots, not free-form quantities, so the raw formula result has to be rounded down to a whole number of lots. Calculate the ideal quantity first, divide by the lot size, then round down. Rounding up quietly increases your risk above the limit you set.
It means the trade does not fit your risk limit — the stop is too wide for your capital. The correct response is to skip the trade or find a tighter technically valid stop. Taking one lot anyway means risking more than your stated maximum, which is the most common way F&O accounts are damaged.
No. Position size is determined by the distance to your stop-loss, not by how much margin the broker will extend. Leverage changes the capital required to hold the position; it does not change how much you lose if the stop is hit. Sizing off available margin instead of risk is what turns one bad trade into a blown account.
Yes for Indian F&O, where STT, exchange charges, stamp duty and GST are material on a round trip. A stop that looks like a 1% loss can settle closer to 1.2% once charges are applied. Sizing slightly below your limit absorbs this.
A fixed percentage compounds with the account: risk shrinks automatically during drawdowns and grows as the account recovers. A fixed rupee amount keeps risking the same figure while the account falls, so the effective percentage rises exactly when you can least afford it.
Lot size is set by the exchange — a fixed number of units in one contract — 65 for Nifty as of January 2026. Position size is your decision: how many of those lots to trade given your capital and stop. The calculator converts your risk limit into lots using the current lot size.
Calculating the right size is the easy half. The hard half is finding out whether you actually traded it — CernoQuant reads your executed trades and measures how far your real position sizes drifted from your own rules.
Track your position sizing automatically in CernoQuant →