IPO Lot Size Calculation: How Minimum Bid Lots, Retail Limits and the SME Two-Lot Rule Work

IPO lot size calculation is the bit of an IPO most people skip. You open your broker app, the minimum quantity is already filled in, you tap apply, and that’s that. But the lot size quietly decides how much money gets blocked, how many applications you can split into, which investor category you land in, and, when an issue is heavily oversubscribed, what your real odds of allotment are. It’s simple arithmetic once you see where the numbers come from.

This guide works through the rules for mainboard IPOs, the retail and non-institutional cut-offs, and the two-lot rule that now applies to SME issues. We use a made-up company with round numbers so you can check every step with a calculator.

Where the lot size comes from

The starting point is SEBI’s own rule for mainboard issues. In its General Information Document for investing in public offers, SEBI says the issuer, in consultation with the book running lead managers, decides the minimum number of shares per bid so that the minimum application value falls between ₹10,000 and ₹15,000. That minimum quantity is the minimum bid lot, and every bid after it moves in multiples of the same lot.

So the lot is not picked out of thin air. It is the price band working backwards. If the share is cheap, the lot holds many shares. If the share is expensive, the lot shrinks to a handful.

The same document says the price band and the minimum bid lot have to be announced in an advertisement in at least one English, one Hindi and one regional newspaper, at least two working days before an IPO opens. That ad, and the red herring prospectus, are where you find the official lot. A broker app or a news summary is only repeating it.

The basic formula

For a mainboard IPO, the calculation goes like this:

• Take the upper end of the price band (the cap price).
• Divide ₹15,000 by the cap price and round down. That gives the largest lot that keeps one application at or under ₹15,000.
• Check that the same lot, priced at the floor of the band, still comes to at least ₹10,000.

Anything between those two limits works. The issuer and the bankers pick one number inside that window.

A worked IPO lot size calculation

Say a hypothetical company, Kaveri Agro Foods Ltd, launches a mainboard IPO with a price band of ₹285 to ₹300 per share.

• At the cap price of ₹300, ₹15,000 buys 50 shares (15,000 ÷ 300 = 50). Fifty-one shares would cost ₹15,300, which is over the limit.
• At the floor price of ₹285, 50 shares cost ₹14,250. That is comfortably above ₹10,000.
• Go the other way and the smallest lot that clears ₹10,000 even at the floor is 36 shares (36 × 285 = ₹10,260; 35 shares would be ₹9,975).

Any lot from 36 to 50 shares satisfies the rule at both ends of the band. In our example, Kaveri’s bankers pick 50. One lot therefore costs ₹15,000 at the cap price, and that is the amount your bank blocks for a single lot if you bid at the cut-off price.

Why the cap price? Because SEBI’s document says that when a retail investor bids at cut-off, the amount is blocked based on the cap price. You are agreeing to pay whatever final price comes out of the book, so the system blocks enough to cover the worst case. If the issue later prices at ₹290 and you get one lot, you pay 50 × ₹290 = ₹14,500 and the rest of the blocked amount is released. We covered how that bid works in more detail in our guide to the IPO cut-off price.

The lot size is just the price band working backwards from a ₹10,000 to ₹15,000 ticket. Once you see that, every other limit in the IPO form is a multiplication problem.

How many lots a retail investor can apply for

The second limit that matters is ₹2 lakh. SEBI’s document defines a retail individual investor as someone who applies or bids for a value of not more than ₹2,00,000, and it says retail bids must be sized so that the bid amount, less any discount, does not cross that figure.

Back to Kaveri at ₹15,000 per lot:

• ₹2,00,000 ÷ ₹15,000 = 13.33, so the most a retail investor can bid for is 13 lots.
• 13 lots = 650 shares = ₹1,95,000 at the cap price.
• 14 lots = 700 shares = ₹2,10,000, which is over ₹2 lakh. That bid is no longer retail.

This is why the maximum retail quantity in a broker app often looks like an odd number. It is simply the biggest whole number of lots that fits under ₹2 lakh at the cap price.

There is a catch people miss. SEBI’s document says that if a retail bid goes above ₹2 lakh because of a revision or any other reason, it may be treated as a non-institutional bid instead, and if it was placed at cut-off, it may be rejected. Non-institutional investors are not allowed to bid at cut-off. So if you are near the ceiling, leave yourself a margin rather than revising upwards at the last minute.

Why one lot can be as good as thirteen

Here is where lot size changes the way we should think about an IPO application. When the retail portion is oversubscribed, SEBI’s document lays out a specific method. The shares available to retail investors are divided by the minimum bid lot. That gives the maximum number of retail investors who can each get one lot, which the document calls the Maximum RII Allottees.

• If the number of valid retail applicants is equal to or less than that maximum, everyone gets one minimum lot first, and the remaining retail shares are shared out proportionately among those who bid for more.
• If there are more applicants than that, who gets the minimum lot is decided by a draw of lots.

Let’s run it for Kaveri. Assume, purely for the example, that 7,00,000 shares are available in the retail category.

• 7,00,000 ÷ 50 = 14,000. That’s the maximum number of retail applicants who can get one lot.
• Now assume 2,80,000 valid retail applications come in. That is far more than 14,000, so the allotment goes to a draw.
• 14,000 ÷ 2,80,000 = 0.05. Each valid application has roughly a 1 in 20 chance of getting one lot.

Notice what does not appear in that maths: the number of lots each person bid for. An applicant who blocked ₹1,95,000 for 13 lots and one who blocked ₹15,000 for a single lot go into the same draw for the same single lot. In a heavily oversubscribed issue, bidding for more lots mostly means more money sitting blocked for a few days.

Flip the scenario. If only 10,000 people applied, all 10,000 would get one lot first. That uses 5,00,000 shares (10,000 × 50). The remaining 2,00,000 shares would then go proportionately to those who asked for more than one lot. In that case, a bigger bid does buy you more shares.

Our explainer on the IPO basis of allotment goes through how the registrar publishes these numbers after the issue closes.

In an issue that is oversubscribed by applicants, thirteen lots and one lot buy the same lottery ticket. The extra lots only matter when there are enough shares to go round.

Above ₹2 lakh: the non-institutional bands

Once a bid crosses ₹2 lakh it moves into the non-institutional investor (NII) category, often called HNI. SEBI’s document says NII and QIB bids must be for a minimum number of shares such that the bid amount exceeds ₹2,00,000, and in multiples of the lot after that.

SEBI later split this category. Its April 2022 board memo on the public issue framework describes a sub-category for applications above ₹2 lakh and up to ₹10 lakh, with at least one-third of the total NII quota set aside for it. The same memo describes moving NII allotment away from a proportionate method to a draw of lots, in the same way retail allotment works.

For Kaveri, the bands work out like this:

• Smallest NII bid: 14 lots = 700 shares = ₹2,10,000.
• Largest bid in the ₹2 lakh to ₹10 lakh band: ₹10,00,000 ÷ ₹15,000 = 66.67, so 66 lots = 3,300 shares = ₹9,90,000.
• From 67 lots (₹10,05,000) upwards, the bid sits in the bigger NII band.

Same idea as retail. The lot size and the price set the boundaries, and the category you fall into follows directly from how many lots you choose.

SME IPOs: the two-lot rule

SME issues used to be different in size but similar in structure. That changed in 2025. An NSE circular dated June 18, 2025, issued after SEBI amended the ICDR Regulations, sets out the new bidding process:

• The retail individual investor category in SME IPOs is replaced by an Individual Investor category.
• The minimum bid for an Individual Investor is 2 lots, with a minimum application size above ₹2 lakh.
• Bidding at the cut-off price is not available in any category.
• Bids cannot be revised downwards or cancelled.
• On the last day, bidding closes at 4:00 PM for all categories, and UPI mandates can be accepted until 5:00 PM.
• QIBs and NIIs apply for more than 2 lots.

The circular says this new process is mandatory for all SME IPOs opening on or after July 1, 2025.

Try it on a hypothetical SME issue. Suppose Sona Packaging Ltd prices its SME IPO at ₹120 per share with a lot of 1,200 shares. One lot costs ₹1,44,000. Two lots cost ₹2,88,000, which is above ₹2 lakh, so that is the smallest application an individual can make. Three lots or more and the same person is bidding in the NII category.

That is a big jump from the ₹15,000 ticket on a mainboard issue, and it is deliberate. The minimum cheque on an SME IPO is now well into the lakhs, and you cannot bid at cut-off or pull out later. Our IPO investing in India guide covers the wider differences between mainboard and SME issues.

A quick checklist before you apply

• Read the lot size and price band from the price band advertisement or the RHP, not from a forwarded message.
• Multiply the lot by the cap price. That is your per-lot block amount if you bid at cut-off.
• For retail, divide ₹2 lakh by the per-lot amount and round down. That’s your ceiling. Leave some margin if you might revise.
• In a hot issue, remember the draw is for one minimum lot per applicant. More lots means more cash blocked, not better odds.
• For SME issues, budget for at least 2 lots above ₹2 lakh, and be sure before you bid, because there’s no downward revision or cancellation.

The short version

A mainboard IPO lot is sized so one application costs between ₹10,000 and ₹15,000. Divide ₹15,000 by the cap price, round down, and you have the lot. Retail investors can go up to ₹2 lakh, which for a ₹15,000 lot means 13 lots. Above that you are an NII, with a separate band up to ₹10 lakh. In an oversubscribed issue, retail allotment is a draw for one lot per applicant, so a single lot has the same chance as thirteen. SME IPOs now start at 2 lots worth more than ₹2 lakh, with no cut-off bidding and no cancellation.

Disclaimer: This article is for information and education only and is not investment advice or a recommendation to apply for, buy or sell any security. Kaveri Agro Foods Ltd, Sona Packaging Ltd and all prices, lot sizes, share counts and application numbers in the examples are hypothetical. Regulatory details are from SEBI’s General Information Document for investing in public offers, SEBI’s April 2022 board memo on the public issue framework and NSE circular NSE/IPO/68604 of June 18, 2025, all linked above. Always check the offer document of the specific issue, and consult a SEBI-registered investment adviser before making investment decisions.