Short answerMax lots = your rupee risk ÷ (entry premium − stop-loss premium) ÷ lot size, rounded down. Example: ₹3,000 risk, entry ₹120, stop ₹90 and a 65-unit lot loses ₹1,950 per lot. That allows 1 lot.
How to use this calculator
Pick buying or selling. Type your capital and the percent of it you will risk on this one trade. Then type the premium you plan to enter at, the premium where you will exit if you are wrong, and the lot size of your contract.
The result panel updates as you type. It shows your risk in rupees, the loss on one lot at your stop, the most lots your rule allows, the capital you need and your actual risk. If something is off, such as a stop above your entry on a bought option, it tells you in plain words.
The formula
Risk per lot = (entry − stop-loss) × lot size
Max lots = floor(risk in ₹ ÷ risk per lot)
Capital needed (buying) = lots × entry × lot size
Actual risk = lots × risk per lot
"Floor" means round down. You cannot trade part of a lot, and rounding up would break your rule. That is why your actual risk is usually a little below your risk budget.
Worked example
Capital is ₹3,00,000. Risk is 1%. You plan to buy an option at ₹120 premium with a stop-loss at ₹90. Lot size is 65 (example only).
- Risk in rupees: ₹3,00,000 × 1% = ₹3,000.
- Risk per lot: (120 − 90) × 65 = ₹1,950.
- Max lots: 3,000 ÷ 1,950 = 1.54, rounded down to 1 lot.
- Capital needed: 1 × 120 × 65 = ₹7,800.
- Actual risk: ₹1,950, which is 0.65% of capital.
Now move the stop to ₹100. Risk per lot becomes 20 × 65 = ₹1,300. Max lots is 3,000 ÷ 1,300 = 2 (rounded down). Capital needed is ₹15,600 and actual risk is ₹2,600, or 0.87%. A tighter stop allows more lots for the same rupee risk, but a stop that is too tight gets hit by normal noise. Place the stop where your idea is wrong, then size from that.
What about selling options?
When you sell an option, you lose if the premium rises. So the stop-loss premium must be above your entry. The tool then works out the loss per lot the same way, using the gap between the two premiums.
The tool does not work out margin for sold options. A sold option can lose far more than the premium you collected, and a gap can take the price through your stop. Use your broker's margin calculator.
Why this matters
The SEBI study for FY26 found that 87.7% of individual F&O traders lost money. The average loss was ₹1.17 lakh, as reported in the press. Barber and Odean (2000) found that households that trade a lot earn lower returns after costs. Size is one of the few things you control.
Fixing the loss before the trade also removes a bad habit: picking the lot count by feel, then moving the stop when price goes against you. Decide the loss first. Then the lots follow. For your total loss across a day, use the daily loss limit calculator. Also read about revenge trading, overtrading and the kill switch.
Source: SEBI study of individual F&O traders for FY26, as reported in the press. Barber, B. and Odean, T. (2000), "Trading Is Hazardous to Your Wealth", Journal of Finance.
Common questions
How many lots should I trade?
Take the rupee amount you accept to lose on one trade. Divide it by the loss per lot if your stop-loss is hit. Round down to a whole number. That is the most lots your risk rule allows. If the answer is 0, one lot is too risky for your rule at that stop.
What is the lot size for Nifty or Bank Nifty options?
Lot sizes are set by NSE and they change from time to time. We do not store them on this page. Check the current lot size for your exact contract on the NSE website or in your broker app, then type it into the lot size box.
Does this work for option selling?
Partly. Choose the selling toggle and the tool works out the loss per lot from your entry and a stop-loss premium above it. It does not work out margin. Margin for sold options depends on the contract, the strike and market conditions. Use your broker's margin calculator.
Is my stop-loss premium a guaranteed loss limit?
No. The tool assumes you exit at your stop-loss premium. In fast markets, or with gaps, your exit can be worse. Option prices can also jump past your stop. Treat the result as a plan, not a promise.
Why is the max lots answer 0?
It means the loss on one lot at your stop is more than the rupee risk you set. You can widen your risk budget, move your stop closer to your entry, pick a cheaper contract or trade a smaller lot size. Do not raise your risk just to make the answer 1.
Size the trade. Then guard the day.
TradeGuard AI watches your broker account and can auto-exit your open positions when you reach your daily loss limit on Dhan. It is part of the Guard plan, launching soon. It does not block your orders. Join the waitlist.
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