PaisaOrbit 
By the PaisaOrbit Research Desk. This article is for educational purposes only and does not constitute investment advice — see the disclaimer at the end.
If you've placed a Nifty 50 F&O order recently and the numbers looked different from what you remembered, you're not imagining it. Two real rule changes reshaped Nifty options and futures trading heading into 2026: NSE's single weekly expiry rule and a revised Nifty lot size of 65. This guide walks through both, with actual worked numbers, so you can adjust your position sizing and expiry-day plan correctly.
What Actually Changed in 2026
- NSE now offers a weekly expiry on only one benchmark index — and on NSE, that's Nifty 50.
- Bank Nifty, Nifty Financial Services (FinNifty), and Nifty Midcap Select lost their weekly contracts — they trade monthly only now.
- Nifty's expiry day moved from the old Thursday slot to Tuesday.
- The Nifty 50 lot size was revised from 75 to 65, effective for contracts expiring January 2026 onward.
- Bank Nifty's lot size dropped from 35 to 30; FinNifty from 65 to 60; Nifty Midcap Select from 140 to 120.
Why SEBI Made These Changes
Before this change, multiple exchanges ran weekly expiries on different indices, stacking expiry-day volatility onto retail traders almost every day of the week. SEBI flagged this concentration of short-tenor, high-theta-decay contracts as a source of outsized retail losses and systemic risk. Limiting each exchange to a single weekly-expiry benchmark index was meant to concentrate that risk into fewer, more predictable sessions rather than eliminate it entirely — the risk in a Tuesday Nifty expiry hasn't gone away, it's just no longer spread across five different weekly contracts.
The Nifty 50 Lot Size Change: From 75 to 65
NSE periodically revises index lot sizes to keep a contract's notional value (lot size × index level) within a band regulators consider appropriate for retail participation. As Nifty's index level has risen over time, the older 75 lot size pushed notional contract value higher than the target band — so NSE reduced the lot size to 65 to bring it back down.
A number of trading blogs describe this change as increasing your capital requirement. That's backwards. A smaller lot size at the same index level means a smaller contract, not a bigger one — check the actual math below before you resize a position based on secondhand claims.
How the New Lot Size Actually Affects Your Margin
Here's the part worth getting right, since it directly determines how much capital a single lot ties up.
- At the old lot size, every 1-point move in Nifty 50 changed your P&L by ₹75 per lot.
- At the new lot size, every 1-point move changes your P&L by ₹65 per lot — a smaller swing per lot, not a bigger one.
- Illustrative example: with Nifty around 25,000, notional contract value moved from roughly 75 × 25,000 = ₹18.75 lakh to 65 × 25,000 = ₹16.25 lakh — about 13% lower.
- Since SPAN + exposure margin scales with notional value, margin per lot fell by a similar ~13% alongside it.
The practical effect: the same capital now lets you hold roughly the same (or slightly more) notional exposure than before, not less. Always confirm the live figure on your broker's margin calculator before placing a trade — SPAN margin moves with volatility day to day, so treat any number here as illustrative, not a quote.
The Single Weekly Expiry Rule, Explained
On NSE, Nifty 50 is now the only index with a weekly contract, expiring every Tuesday. Monthly, quarterly, and half-yearly Nifty contracts also expire on the last Tuesday of their respective periods. Bank Nifty, FinNifty, and Nifty Midcap Select are monthly-only now, each expiring on the last Tuesday of the month.
For anyone who built a routine around Thursday Nifty expiries or weekly Bank Nifty trades, this is the single biggest habit to unlearn for 2026: Tuesday is now expiry day, and weekly Bank Nifty contracts simply don't exist anymore.
What This Means for Bank Nifty, FinNifty, and Midcap Select Traders
- No more weekly theta plays on these three indices — every strategy that relied on Thursday-to-Thursday weekly decay now has to be rebuilt around a monthly cycle.
- Wider strike gaps near expiry are common on monthly-only contracts simply because there are fewer expiry cycles concentrating liquidity.
- Gamma risk is more concentrated in the final days before a monthly expiry than it was under weeklies, since there's no earlier weekly expiry to "reset" positioning first.
If your strategy specifically depended on Bank Nifty's old weekly cadence, the honest move is to either rebuild it for monthly expiry, or shift that specific strategy to Nifty 50, which kept its weekly contract.
Adjusting Your Nifty Expiry-Day Strategy for 2026
- Re-check position sizing. The ₹65-per-point lot value means a position sized for the old ₹75-per-point lot will now be slightly under-leveraged in rupee terms for the same number of lots — decide deliberately whether you want to add lots to match your old rupee exposure, or keep the lower exposure.
- Move your calendar to Tuesday. Pre-expiry IV crush, theta acceleration, and pin-risk behavior now cluster around Tuesday, not Thursday.
- Re-test calendar spreads. Indian brokers apply stricter margin rules in the final hours before expiry — a spread that held together comfortably under the old cycle may get flagged differently now; check your broker's specific expiry-day margin policy.
- Watch where price is gravitating, not just the clock. Reading support and resistance levels around the expiry strike still matters as much as the calendar change itself — a level that's held three times intraday is still a level, Tuesday or Thursday.
Worked Example: Sizing a Nifty Position Under the New Rules
Say a trader previously bought 2 lots of Nifty futures at the old 75 lot size — a 150-unit position. To hold the same 150-unit exposure under the new 65 lot size, they'd need to buy roughly 2.3 lots — in practice, rounding to 2 lots gives 130 units (a slightly smaller position) or 3 lots gives 195 units (a larger one). There's no exact match anymore; every position size decision now involves this rounding step, however small.
| Metric | Old (lot size 75) | New (lot size 65) |
|---|---|---|
| Value per 1-point move | ₹75 | ₹65 |
| Notional value @ Nifty 25,000 | ₹18,75,000 | ₹16,25,000 |
| Approx. margin change | Baseline | ~13% lower |
| 2-lot position size | 150 units | 130 units |
Quick Reference: 2026 Index Lot Size Changes
| Index | Old lot size | New lot size | Weekly expiry? |
|---|---|---|---|
| Nifty 50 | 75 | 65 | Yes — every Tuesday |
| Bank Nifty | 35 | 30 | No — monthly only |
| Nifty Financial Services (FinNifty) | 65 | 60 | No — monthly only |
| Nifty Midcap Select | 140 | 120 | No — monthly only |
Common Mistakes to Avoid
- Assuming margin went up. As shown above, it went down — don't resize a position based on outdated blog posts (including, until now, some describing this exact change).
- Trading Bank Nifty on a Thursday habit. There is no Thursday weekly Bank Nifty contract anymore — check the actual expiry calendar before entering.
- Ignoring the rounding gap. 75 doesn't divide evenly into 65-based lots — recalculate exact exposure rather than assuming "2 lots" still means what it used to.
- Skipping the live margin calculator. SPAN margin changes with volatility daily — the percentages here are illustrative, not a substitute for your broker's real-time figure.
Frequently Asked Questions
What is the new Nifty 50 lot size in 2026?
65 units per lot, effective for all contracts expiring from January 2026 onward. Contracts that expired up to December 2025 used the older 75 lot size.
Did the Nifty lot size change increase or decrease margin requirements?
It decreased them. A smaller lot size at the same index level means a smaller notional contract value, so SPAN and exposure margin per lot dropped by roughly 13%.
Which index still has weekly expiry on NSE?
Only Nifty 50. Bank Nifty, Nifty Financial Services, and Nifty Midcap Select are monthly-only now.
What day does Nifty 50 expire on now?
Tuesday — weekly, monthly, quarterly, and half-yearly Nifty contracts all expire on a Tuesday (the last Tuesday of the period, for monthly and longer contracts).
Disclaimer
This article is for educational purposes only and does not constitute financial, investment, or trading advice. Futures and options trading involves substantial risk of loss and is not suitable for every investor. Lot sizes, margin rules, and expiry schedules are set by NSE/SEBI and can change again — always verify current figures on the official NSE website and your broker's platform before trading. PaisaOrbit is not a SEBI-registered investment advisor.