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Lot size is the fixed number of units one options contract represents — the number every strategy example on this site multiplies premiums and payoffs by. It isn't permanent: NSE periodically revises it, most recently in January 2026.

You can't trade a single unit of a Nifty option — contracts trade in fixed lots, and the lot size is how many index units that one contract represents. The current Nifty lot size is 65, which is the figure used consistently throughout every strategy and Greek worked example on this site. Every premium, every max profit and max loss figure shown elsewhere on this site is the per-share number multiplied by this lot size.

NSE periodically revises lot sizes to keep each contract's notional value (roughly, the index level multiplied by the lot size) within a band SEBI considers appropriate — not too small (which would make contracts trivially cheap to trade, encouraging excessive speculation) and not too large (which would price out smaller participants). As the index level itself drifts up over time, the lot size is periodically revised downward to keep the notional value from drifting too far outside that target range. The most recent such revision cut the Nifty lot size from 75 to 65, effective January 2026.

Using the same at-the-money call premium (145) used throughout this site's own strategy examples, at Nifty 24,000:

At the same premium, the revision reduced the cost of one lot by ₹1,450 — about 13.3% smaller. This is a direct, mechanical effect of the lot size change itself, separate from anything the market did — the same option, same strike, same premium, simply now represents fewer units per contract.

• Every max profit, max loss, and breakeven figure on this site scales directly with lot size — the per-share numbers shown in each worked example need to be multiplied by whatever the current lot size actually is to reflect a real position.
• SPAN margin also scales with lot size, covered on the SPAN Margin page — a lot size revision changes both the position's cost and its margin requirement together.
• A past lot size revision can make older content (including screenshots, forum posts, or older strategy writeups) use stale multipliers — worth checking which lot size any given source assumes before applying its numbers directly.

• Lot size is not fixed forever — it has been revised before and will likely be revised again as the index level changes over time. Always confirm the current lot size before sizing a real position.
• A lot size change doesn't reflect any view on the underlying — it's a contract specification adjustment, not a signal about where Nifty is headed.
• Existing open positions get transitioned to a new lot size on the effective date set by the exchange — worth checking exchange circulars around any announced change if holding positions through the transition.