'Math changes but not discipline,' analysts advise F&O traders amid reduction in lot sizes of four NSE indices

'Math changes but not discipline,' analysts tell F&O traders amid reduction in lot sizes of four NSE indices

• NSE to reduce lot sizes for major indices from December 2025 expiry cycle
• Nifty 50 lot size cut to 65, Bank Nifty to 30, others also reduced
• Traders must adjust strategies; smaller lots mean lower capital and margin needs

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With lot sizes of four NSE indices being revised on the lower side from December 31, market experts advised F&O (futures & options) traders to stick to discipline.

In October, the National Stock Exchange (NSE) had announced a revision in the market lot sizes of several major index derivative contracts, with the changes scheduled to take effect after the December 2025 expiry cycle. As per the circular, the lot sizes for Nifty 50, Nifty Bank, Nifty Financial Services, and Nifty Midcap Select will be reduced. The Nifty 50 lot size will be revised from 75 to 65, Nifty Bank from 35 to 30, Nifty Financial Services from 65 to 60, and Nifty Midcap Select from 140 to 120. NSE also clarified that the lot size for Nifty Next 50 will remain unchanged.

Analysts weighed on what this would mean for the derivative traders.

"The reduction in the number of lots of Nifty, Bank Nifty, and other NSE indices results in the reduction of the notional value of the contract, and it will have a straight effect on the capital employed by the traders. Reducing the number of lots of Nifty from 75 to 65 and Bank Nifty from 35 to 30 will make the traders adjust their position sizing, but it will have a positive effect on the involvement of traders in the F&O segment," said Siddharth Maurya, Founder & Managing Director, Vibhavangal Anukulakara Pvt Ltd.

Another analyst said "smaller contracts change the math, not the discipline" alluding to the volatile nature of F&O trading, which could cause swift erosion of capital.

SEBI data shows 90% F&O traders make no profit at all.

"The revision lowers per-contract exposure and margin requirements, improving capital efficiency and execution flexibility. However, it also renders many existing quantity-based calculations obsolete.

"Payoff profiles, option Greeks, hedging ratios, breakeven points, and portfolio exposure will all shift under the new lot structure. Traders and market participants will need to recalibrate strategy parameters using rupee risk and total exposure as the primary reference, rather than the number of lots traded.

"While smaller lot sizes may enhance liquidity, depth, and execution quality, they should not be mistaken for reduced risk. The regulatory intent is improved risk management—not higher aggregate exposure.

"Smaller contracts change the math, not the discipline. Just because contracts are smaller doesn’t mean one should trade more of them," said Tushar Badjate: Director and Compliance Officer, Badjate PMS.

From the next cycle, the January 2026 weekly and monthly contracts will reflect the revised market lots. The monthly contracts will shift to the revised structure after the December 30, 2025 expiry, with the January 27, 2026 expiry carrying the updated lot sizes.

Traders will need to adjust position sizes and margin requirements, while retail investors may find contracts more accessible as they will need lesser capital.

Option sellers must be cautious, as collecting the same premium will require more lots, increasing transaction costs, said an analyst about the revised lot sizes.

"By reducing the lot size (e.g., Nifty from 75 to 65), the exchange is bringing the notional contract value back into the optimal Rs 15 lakh – Rs 17 lakh range. It reduces per-point P&L by roughly 10–15%, making contracts more affordable but requiring strategic adjustments. Traders should recalibrate position sizing in rupee terms rather than lot counts to maintain consistent risk and returns. Option sellers must be cautious, as collecting the same premium will require more lots, increasing transaction costs; shifting to slightly higher delta strikes, spread-based strategies, or fixed-fee brokers can help preserve efficiency.

"Scalpers and intraday traders need to reset their mental P&L calculations to avoid underestimating risk and rewards. During the initial transition phase, using limit orders is advisable due to potential liquidity and spread disruptions. Finally, investors using derivatives for hedging must recalculate hedge ratios, as lower contract values will require more lots to achieve the same portfolio protection," said Santosh Meena, Head of Research at Swastika Investmart.

The NSE revises lot sizes of Futures & Options contracts primarily to keep the contract value within a standard range, to keep the contracts affordable and standardized. Since derivatives are leveraged instruments, traders do not have to pay the full value of the contract upfront, but the lot size determines their exposure and the margin required. The NSE undertakes lot size revisions to ensure market efficiency and liquidity, and to contracts more acceptable for a broader set of market participants.

Also, from December 31, Bank Nifty will function with 14 constituents instead of the existing 12.