Introductory Context
"The lot size question -- what is the current lot size for each index and how does it translate into the order form's quantity field -- is the most practically important operational knowledge for new options traders. SEBI periodically revises lot sizes when index levels change significantly (the revision typically brings the per-lot value closer to a target notional value). Always verify the current lot size before placing any trade, and always translate lots to units before entering the quantity in the order form. "
Current NSE Index Option Lot Sizes
The current lot sizes for NSE index options, as revised following SEBI's November 2024 framework update: Nifty 50 -- 75 units per lot. Bank Nifty -- 30 units per lot (revised from 25 in the November 2024 update). FinNifty -- 65 units per lot. Midcap Nifty -- 50 units per lot. Sensex (BSE) -- 20 units per lot. These lot sizes apply uniformly to all weekly and monthly expiry contracts for each index.
For individual stock options, lot sizes vary significantly and are specific to each stock. HDFC Bank lot size: 550 units. Reliance Industries: 250 units. Infosys: 300 units. TCS: 150 units. SBI: 1,500 units. These stock-specific lot sizes must be verified on the NSE website (nseindia.com → Derivatives → Contract Specification) before placing any stock option order. Never rely on memory for stock option lot sizes -- they are periodically revised and the consequences of using an outdated lot size in position sizing calculations are significant.
Lot Size to Quantity Conversion -- Always Verify Before Ordering
Nifty 50: 1 lot = 75 units. 2 lots = 150 units. 3 lots = 225 units. Bank Nifty: 1 lot = 30 units. 2 lots = 60 units. 3 lots = 90 units. FinNifty: 1 lot = 65 units. Midcap Nifty: 1 lot = 50 units. Verify current lot sizes at: NSE India website (nseindia.com) → Market Data → Derivatives → Contract Specifications. SEBI periodically revises lot sizes. The curriculum quotes these as current at time of writing; always check NSE for the authoritative current figure before trading.
Why SEBI Revises Lot Sizes
SEBI revises index and stock option lot sizes when the notional value per lot drifts significantly from a target range (approximately Rs 5 lakh to Rs 10 lakh per lot at the current index level). As Nifty rises from 18,000 to 24,000, the notional value per Nifty lot at the old lot size increases proportionally -- eventually exceeding the target range. SEBI then reduces the lot size to bring the per-lot notional value back within range. The November 2024 revision adjusted Bank Nifty's lot size from 25 to 30 units specifically to address this drift. Lot size revisions affect position sizing calculations, margin requirements, and per-lot premium cost simultaneously.
The Five Most Common Order Entry Mistakes
Mistake 1 -- Entering lots instead of units: The most common and most consequential error. A trader intending to buy 2 Nifty lots enters 2 in the Qty field. The system fills 2 units at Rs 90 per unit = Rs 180 total cost. The intended position (150 units at Rs 90 = Rs 13,500) was not entered. The position appears in the Positions tab as a tiny 2-unit holding -- not visible as an error until the position is compared to the intended size.
Mistake 2 -- Wrong expiry selection: Selecting the monthly expiry when the weekly was intended, or vice versa. Monthly Nifty options typically cost three to four times more per unit than weekly options at the same strike. This error is caught by the 2 percent position sizing check if conducted properly -- the total cost of the incorrectly selected contract will exceed the calculated maximum. Prevention: verify the expiry date (not just the expiry category) in the order form before clicking Buy.
Mistake 3 -- Wrong strike price: Selecting a strike one increment away from the intended strike. For Nifty, where strikes are typically at 50-point intervals, selecting 23,100 instead of 23,050 or 23,050 instead of 23,000 moves the break-even level by 50 points -- significant for ATM options but potentially much more significant for OTM options where the difference in premium between adjacent strikes is proportionally larger.
Mistake 4 -- CE when PE intended (or vice versa): Selecting a call when a put was intended. This error is not caught by any automatic validation -- both CE and PE are valid contracts that will fill at market prices. The error typically becomes apparent immediately after the fill when the position's P&L moves in the opposite direction from expected on any underlying move. The only prevention is explicit verification of the CE/PE designation in the order form before submission.
Mistake 5 -- MIS instead of NRML for overnight positions: Selecting the intraday product type for a position intended to be held overnight. The broker's auto square-off mechanism will close the position at approximately 3:15 to 3:25 PM regardless of the current P&L. This error causes an unintended exit at an arbitrary intraday price rather than at the defined stop or target. Prevention: always verify the Product field (NRML/D) before submitting any order intended to be held overnight.
The Quantity Verification Formula -- Do This Before Every Order
Before clicking the Buy or Sell button on any options order: Intended lots x lot size = required quantity. Verify this number appears in the Qty field. If the Qty field shows a different number, do not submit until it is corrected. This five-second verification prevents the most common and most invisible order entry error. For Nifty: intended 2 lots x 75 = 150. If Qty shows 2, it is wrong. If Qty shows 150, it is correct. Make this calculation automatic before every single order.
THE INVISIBLE ERROR -- A REAL ACCOUNT IMPACT
Rahul entered what he believed was a 2-lot Nifty call position at 9:35 AM. The order filled immediately for Rs 180 (2 units at Rs 90). Nifty subsequently rose 250 points over the session. By 2:30 PM, the option had risen to Rs 155. Rahul's 'position' showed a gain of Rs 130 (2 units x Rs 65 gain). He had expected a gain of approximately Rs 4,875 (150 units x Rs 65). The discovery of the lot size error occurred at exit when the P&L was Rs 130 instead of the expected Rs 4,875. The 2-unit position had not consumed any meaningful capital (Rs 180 cost vs Rs 13,500 intended) but had also produced a negligible gain relative to the analytical effort invested in identifying the trade.
SEBI's Lot Size Revision Process - How to Stay Current
SEBI revises lot sizes through circulars published on the SEBI website (sebi.gov.in). NSE implements the revised lot sizes from the specified effective date, after which new contracts use the revised lot size while existing contracts (already issued under the prior lot size) continue at the prior lot size until their expiry. This transition period means that during the week of a lot size revision, the option chain may show contracts at both the old and new lot sizes for overlapping expiry periods.
The safest practice during a lot size revision period: check the contract specification in the NSE option chain directly for each specific contract before placing any order. The option chain's contract detail view shows the lot size for each specific contract explicitly -- this is the authoritative source during any period when lot sizes may be in transition.
Save the Lot Size Reference in Your Trading Journal Header
In the Traders Diary session header (the pre-market account status check), add a 'Current Lot Sizes' field. At the start of each month, verify the current Nifty and Bank Nifty lot sizes against the NSE website and update the field. With the lot sizes visible in the journal header, the pre-order quantity calculation is performed against a verified reference rather than a memorised figure. For traders who also trade stock options, maintain a separate running list of the current lot sizes for each stock in their watch universe.