"Two lots" is an unfinished sentence
Lot count, notional exposure and premium at risk are three different measurements of the same trade.
Contract size is set by the exchange and it moves. From the January 2026 series, NSE cut Nifty from 75 to 65 and Bank Nifty from 35 to 30, with Fin Nifty and Midcap Select also trimmed.
Which means a lot count written in your journal in 2025 does not mean the same thing as the identical number written in 2026.
The three numbers, side by side
Lot count is packaging. Notional is underlying times multiplier times lots, and it is the number that makes retail books look enormous. Premium at risk is what a long option holder can actually lose, plus charges.
A short option has no comparable cap, which is precisely why one blended "risk" field is misleading.
| Contract | Old lot | New lot | Change |
|---|---|---|---|
| Nifty 50 | 75 | 65 | −13.3% |
| Nifty Bank | 35 | 30 | −14.3% |
| Nifty Financial Services | 65 | 60 | −7.7% |
| Nifty Midcap Select | 140 | 120 | −14.3% |
| Nifty Next 50 | unchanged | unchanged | — |
Effective from the January 2026 series, after the December 2025 expiries.
Source: Economic Times — revised index F&O lot sizes, January 2026 series
What changes when the lot shrinks
Every point of index movement is worth less per lot, margin per contract falls, and per-lot P&L from before and after the change is no longer comparable.
If you keep a "P&L per lot" statistic, either normalise it to notional or break the series at the revision date.
Arithmetic, not a forecast. The same move now pays roughly 13% less per lot.
Never rewrite historic quantity
A migration script that multiplies old trades up to the new specification will destroy your risk statistics and your maximum-adverse-excursion history. Keep old fills exactly as they were and annotate the change date.
Key takeaways
- Always pair lot counts with the contract spec of that date.
- Separate notional, premium paid and spread width.
- Break or normalise per-lot series at a lot-size revision.
Where these numbers come from
- Economic Times — revised index F&O lot sizes, January 2026 series
- NSE India — circulars and contract specs
Not advice, not a call. NiyataBook is a personal trading journal, not a SEBI-registered investment adviser or research analyst. Everything above looks backwards at trades that already closed. What happened in a book does not promise what happens next, and F&O can take a year’s savings in a week.