Lot size is the fixed number of units in one futures or options contract. In 2026, one Nifty lot is 65 units and one Bank Nifty lot is 30.
Lot size is the fixed number of units of the underlying that make up one futures or options contract. The exchange sets it for every stock and index in the F&O segment. You can only trade in whole lots, so your quantity is always the number of lots multiplied by the lot size, and your premium, margin and profit or loss all scale with it.
Quantity = number of lots × lot size
Contract value = lot size × price of the underlying
Lot sizes are set by the exchange and revised from time to time, so always check the current lot size on your broker’s order screen or the exchange’s contract details before you trade. The examples below use made-up lot sizes and prices to show how lot size affects a trade.
Say an index option has a lot size of 50 and you buy a call at a premium of ₹100 (hypothetical numbers).
You can’t buy 70 units, because 70 isn’t a multiple of 50. Your quantity has to be 50, 100, 150 and so on.
Every rupee the premium moves is multiplied by the lot size. In the same example, if the premium rises from ₹100 to ₹110:
The same works against you if the premium falls. For futures, every 1-point move in the underlying changes the value of one lot by the lot size. Here’s what the same 100-point move means for one lot at three different lot sizes:
| Lot size (hypothetical) | Value of a 1-point move | Value of a 100-point move |
|---|---|---|
| 40 | ₹40 | ₹4,000 |
| 70 | ₹70 | ₹7,000 |
| 80 | ₹80 | ₹8,000 |
The market move is identical in all three rows. Only the lot size changes, and the profit or loss changes in direct proportion to it.
For futures, the margin you need is a percentage of the contract value, and the contract value depends on the lot size. With a hypothetical index at 20,000 and a lot size of 50, one lot has a contract value of 20,000 × 50 = ₹10,00,000.
If the same index had a lot size of 80 instead, one lot would be worth ₹16,00,000, and the margin needed for a single lot would rise in the same proportion. Option buyers don’t pay margin, but option sellers do, and it scales with the lot size in the same way.
Because you can only trade whole lots, lot size decides how finely you can control your risk. Say you’re willing to risk ₹4,000 on a futures trade and your stop-loss is 40 points away (hypothetical numbers):
| Lot size 50 | Lot size 80 | |
|---|---|---|
| Risk per lot (40 points × lot size) | ₹2,000 | ₹3,200 |
| Lots you can take within ₹4,000 | 2 | 1 |
| Actual risk at that size | ₹4,000 | ₹3,200 |
| Risk if you add one more lot | ₹6,000 | ₹6,400 |
With the smaller lot size, two lots use your full risk budget. With the larger one, you can only take one lot, and a second would almost double your risk. The bigger the lot, the bigger the jumps in risk between one lot and the next, which is why position sizing in F&O always has to be planned in whole lots.
Exchanges size each contract so that one lot is worth a broadly similar amount across instruments, within limits set by the regulator. When the price of the underlying moves a long way, the value of one lot drifts, so the exchange revises the lot size:
When a lot size changes, contracts that are already trading usually keep their old lot size until they expire, and only new contracts use the new size. During the changeover, different expiries of the same index can have different lot sizes, so check the lot size of the exact contract you’re trading.
Every stock in the F&O segment has its own lot size. Higher-priced stocks get smaller lots, so contract values stay in a similar range. For example (hypothetical):
| Share price | Lot size | Contract value | |
|---|---|---|---|
| Stock A | ₹500 | 2,000 | ₹10,00,000 |
| Stock B | ₹5,000 | 200 | ₹10,00,000 |
Lot sizes also change after corporate actions. Say a stock at ₹1,000 has a lot size of 500, and it splits so that each share becomes two. The share price drops to around ₹500, so the exchange doubles the lot size to 1,000 and adjusts the strike prices of existing contracts. One lot is still worth about ₹5,00,000, so open positions aren’t changed in value by the split itself.
Stock F&O is physically settled, so lot size also decides how many shares change hands at expiry. An in-the-money stock option or an open stock future held to expiry means delivering or receiving the full lot of shares.
| What it affects | How to work it out |
|---|---|
| Quantity | Number of lots × lot size |
| Premium paid or received | Quantity × premium per unit |
| Profit or loss per ₹1 premium move | Quantity |
| Profit or loss per 1-point futures move | Lot size × number of lots |
| Contract value | Lot size × price of the underlying |
| Margin | A percentage of the contract value |
Very large orders have one more limit. Exchanges set a maximum quantity allowed in a single order, called the freeze quantity. Orders above it are rejected, although many brokers split them into smaller orders automatically.
To see live premiums and open interest for every strike before you work out your position size, open Stolo’s Nifty option chain.
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