Lots in Securities Trading: Round Lot, Odd Lot and the Other Lot Types

A lot is the standard quantity a security trades in. For US stocks, a round lot has meant 100 shares for most of market history, an odd lot is anything smaller, and a mixed lot is a round lot plus an odd lot, such as 250 shares. Since November 3, 2025, the SEC's rules give higher-priced stocks smaller round lots: 40 shares above $250, 10 shares above $1,000 and 1 share above $10,000.

Other markets use the word differently. An options contract covers 100 shares. A futures contract has a fixed size set by the exchange, such as 5,000 bushels of corn. In forex, a standard lot is 100,000 units of the base currency. Bonds have no regulator-set round lot. You can still buy any whole number of shares you like; lot size mostly decides how orders are displayed and priced, not what you are allowed to buy. This page covers each market, then the other meaning of "lot" your broker uses: the tax lot.

What a Lot Means in Trading

The word comes from the old sense of a "lot" as a batch of goods sold together. On an exchange it is the batch size that the market treats as normal. When people search "stock lot meaning" or "what is one lot of shares", the traditional answer is 100 shares, and for any US stock priced at $250 or less, that is still the answer.

A lot does three jobs:

• It standardises quotes. A displayed bid of "5 x 20.10" once meant five round lots, or 500 shares, at $20.10. Everyone reading the quote knew the unit.
• It sets which orders count. Under the SEC's Regulation NMS, quotes of at least a round lot feed the national best bid and offer (NBBO), the reference prices that brokers must respect when they route your order.
• It fixes the contract size in derivatives. An options or futures contract is itself a lot: one contract is a defined quantity that cannot be split.

For an individual investor buying stock, the first two jobs happen in the background. The third matters directly: you cannot buy half an options contract, so the lot size sets the smallest position you can take.

Round Lots, Odd Lots and Mixed Lots in Stocks

Here are the three stock lot types, using the 100-share round lot that still applies to most stocks:

• Round lot: 100 shares or a multiple of 100 (100, 300, 1,200).
• Odd lot: fewer than one round lot, so 1 to 99 shares.
• Mixed lot: more than a round lot but not an even multiple, such as 250 shares (two round lots plus a 50-share odd lot).

The rules changed in 2025. The SEC's definition of "round lot" in Rule 600(b)(93) of Regulation NMS now ties the round lot to each stock's price. For a stock whose average closing price during the prior evaluation period was "$250.00 or less per share," a round lot is 100 shares. From $250.01 to $1,000.00 it is 40 shares. From $1,000.01 to $10,000.00 it is 10 shares. At $10,000.01 or more it is 1 share.

The SEC adopted the accelerated schedule on September 18, 2024, and the adopting release set the round lot definition to take effect on "the first business day of November 2025." In a May 2025 alert, Nasdaq's UTP securities information processor told data vendors that the change would take effect on November 3, 2025, and that consolidated quotes would show sizes in actual shares, rounded down to the nearest multiple of the stock's round lot, rather than in lots of 100.

Each stock's lot is reset twice a year. The primary listing exchange measures the average closing price over all trading days in March, and the new round lot takes effect on the first business day of May. September's average sets the round lot from the first business day of November. A stock that climbs from $240 to $300 and holds there through March moves from a 100-share lot to a 40-share lot in May.

Take a stock that averaged $400 a share in September. Its round lot from November is 40 shares. A 250-share order is now six round lots (240 shares) plus a 10-share odd lot. The same order in a $40 stock is two round lots plus a 50-share odd lot. Your order can fill in any size either way; the difference is in how the market displays and protects it.

For more on how 100 shares became the standard, see our page on round lots.

Why Odd Lots Matter More Than They Used To

Odd lots used to be a sideshow. They were handled by specialist odd-lot dealers, and a whole market-timing idea, the odd-lot theory, grew up around the assumption that small traders buying in odd lots were usually wrong. Today odd lots are the majority of stock trades.

In the 2024 adopting release, SEC staff reported that in 2023 "the daily exchange odd-lot rate for all corporate stocks ranged from approximately 61% to 70% of trades," and for exchange-traded products it ranged from 31% to 42%. The same release cites an earlier staff analysis of May 2020 data: about 45% of on-exchange trades in corporate stocks and ETFs were odd lots, but only about 10% of volume, and 40% of those odd-lot trades executed at a price better than the NBBO. Odd lots are frequent, small and often well priced.

That was the problem the 2025 changes were built to fix. When a round lot is 100 shares of a $900 stock, a displayed quote needs $90,000 behind it, so a better-priced order for 30 shares was invisible to anyone watching the public quote. Smaller round lots for expensive stocks pull more of those orders into the NBBO. Separately, the public data feeds began disseminating odd-lot quotes: from April 27, 2026, the securities information processors carry the best odd-lot bid and offer priced better than the NBBO across all exchanges, plus each exchange's best odd-lot bid and offer at or better than the NBBO.

What this means for you:

• Buying 7 shares is normal. Your broker will fill it, and fractional-share programs go further, down to a slice of one share.
• The quote you see may not show everything. On a data feed that shows only round-lot quotes, better prices for small sizes can exist inside the spread.
• Odd-lot holders sometimes get special treatment. In a company buyback by tender offer, SEC Rule 13e-4 lets the company first accept every share tendered by holders who own no more than a number it specifies (which must be under 100 shares) and tender all of them, before prorating everyone else. Our page on odd lots covers these odd-lot offers.

Lot Size for Bonds

Is there a lot size for a bond? Not in the stock-market sense. There is no single, rule-defined round lot for bonds the way Regulation NMS defines one for stocks. What exists is a set of denominations and market conventions.

• Corporate bonds are usually priced per $1,000 of face value. FINRA's bond basics page explains that quotes are a percentage of par: "A $1,000 bond trading at par is said to be trading at 100."
• US Treasury notes sold through TreasuryDirect have a minimum purchase of $100, in increments of $100.
• Municipal bonds set a minimum denomination at issuance. An MSRB notice describes "the typical $5,000 par value," and some issues are set larger, often $100,000. The same MSRB notice explains that Rule G-15(f) generally bars dealers from selling to customers in amounts below the minimum denomination.

Big trades in bonds run to millions of dollars. FINRA's public TRACE tape shows the exact size of an investment-grade corporate bond trade only up to $5 million of face value; larger trades appear as "$5MM+", and high-yield trades are capped at "$1MM+". Trades far below those sizes are commonly called odd lots. When a firm sells you a bond from its own inventory, FINRA notes, it may "mark up" the price you pay over what it paid. Small trades often carry larger markups per bond than institutional blocks, so compare the price you are quoted with recent TRACE prints before you buy.

Lots in Options Trading

For listed equity options, the contract is the lot. FINRA puts it plainly: "A standard-size options contract is equal to 100 shares of the underlying security." Premiums are quoted per share, so a call quoted at $2.40 costs $240 per contract, before commissions and fees.

That 100-share multiplier sets the minimum stake. Five contracts control 500 shares. If you own 250 shares and want to sell covered calls, you can write two contracts against 200 shares; the other 50 shares cannot be covered by a standard contract. There is no larger options "lot" made of many contracts; one contract is the unit.

Lots in Futures Trading: Contract Sizes

Futures traders say "contract size" rather than lot, but the idea is the same: the exchange fixes how much of the underlying one contract covers. The CFTC's guide to reading futures price tables uses the corn contract as its example: "the contract size is 5,000 bushels." The CFTC's weekly Commitments of Traders report for September 22, 2026 lists contract sizes for other Chicago Mercantile Exchange contracts, among them:

• E-mini S&P 500: $50 times the S&P 500 index.
• Micro E-mini S&P 500: $5 times the index, one-tenth of the E-mini.
• Canadian dollar: CAD 100,000 per contract.
• Euro FX: EUR 125,000 per contract.

Smaller "mini" and "micro" versions exist because a full contract can be too large for many accounts. At an illustrative index level of 6,000, one E-mini controls $300,000 of stock exposure and one Micro E-mini controls $30,000. Commodity markets have their own smaller contracts, covered in our page on job lots.

Forex Lots: Standard, Mini and Micro

In currency trading, a lot is a number of units of the base currency, the first currency in the pair. OANDA's US help pages give the conventions: "1 standard lot = 100,000 units," "1 mini lot = 10,000 units" and "1 micro lot = 1,000 units." Platforms differ. tastyfx's product details say its standard contract is 100,000 of the first-named currency with "a minimum trade size of 0.01 lots (equivalent to 1000 of the first-named currency)," while OANDA's own platform lets you trade in single units and "does not differentiate between standard, mini or micro accounts."

Lot size drives both risk and the cash you must post. In the US, CFTC rule 17 CFR 5.9 sets a floor on the security deposit for retail forex: at least 2% of notional value for major currency pairs and 5% for all other pairs. Dealers can require more.

A worked example, using an illustrative EUR/USD rate of 1.1000:

• One standard lot (EUR 100,000) is $110,000 of notional value. The minimum deposit at 2% is $2,200, and each pip (0.0001) is worth $10.
• One mini lot (EUR 10,000) is $11,000 notional, a $220 deposit and $1 per pip.
• One micro lot (EUR 1,000) is $1,100 notional, a $22 deposit and $0.10 per pip.

A 50-pip move against a standard lot costs $500, about 23% of that $2,200 deposit. The same move costs $5 on a micro lot. Our guide to pips walks through pip values for pairs that do not end in US dollars.

Tax Lots: The Other "Share Lots"

Your brokerage statement uses "lot" in a second sense. A tax lot is each separate purchase of the same security, with its own date and cost. Buy 50 shares in January 2024 and 50 more in March 2026 and you own one position made of two tax lots. This is usually what "share lots" means on a statement or a cost-basis screen.

Which lot you sell sets your gain. IRS Publication 550 says that if you "cannot adequately identify the shares you sell, the basis of the securities you sell is the basis of the securities you acquired first." That default is first in, first out (FIFO). You can instead name the specific shares, by telling your broker which lot to sell at the time of the sale and getting written confirmation.

An example with the two lots above: 50 shares bought at $80 in January 2024 and 50 at $120 in March 2026. You sell 50 shares at $150 in October 2026.

• FIFO sells the $80 lot: a $3,500 gain (50 x $70), long-term because it was held more than a year.
• Specific identification of the $120 lot: a $1,500 gain (50 x $30), but short-term, taxed at ordinary income rates.

Which is cheaper depends on your tax bracket. Our guide to capital gains tax on stocks shows the rate difference.

What Lot Sizes Mean for Your Orders

For most individual investors, lot sizes are background detail. They matter in a few specific places:

• Price display. A round lot on a $600 stock is now 40 shares, so a 40-share bid counts toward the NBBO where it once did not.
• Bond pricing. Small bond trades are priced differently from institutional blocks. Check recent TRACE prints before you buy.
• Derivatives sizing. One options contract is 100 shares; one E-mini is $50 times the index. Know the notional value before you trade.
• Forex leverage. The 2% floor allows up to 50-to-1 on pairs designated as major, but dealers often require more; at tastyfx, for example, GBP/USD and USD/JPY need 5% (20-to-1). Start with micro lots.
• Taxes. Name your tax lots when you sell, or FIFO decides for you.

FAQ

What is a lot in stocks?

A lot is the standard unit for trading shares. For US stocks priced at $250 or less it is 100 shares, called a round lot. Fewer than a round lot is an odd lot, and a round lot plus an odd lot is a mixed lot. You can buy any whole number of shares.

Is a round lot still 100 shares?

For most stocks, yes. Since November 3, 2025, the SEC's Regulation NMS sets 40-share round lots for stocks averaging $250.01 to $1,000, 10 shares from $1,000.01 to $10,000 and 1 share above that. Each stock's lot is reset in May and November.

What is the lot size for a bond?

There is no single official round lot for bonds. Corporate bonds are priced per $1,000 of face value, Treasury notes sell in $100 increments, and municipal bonds usually have a $5,000 minimum denomination. Large dealer trades run to millions of dollars.

How many shares are in one options contract?

A standard listed equity options contract covers 100 shares of the underlying stock, so a premium of $1.50 per share costs $150 per contract.

Sources

• eCFR, 17 CFR 242.600, NMS security designation and definitions: round lot definition (b)(93), evaluation periods and operative dates
• Federal Register via GovInfo, Regulation NMS: Minimum Pricing Increments, Access Fees, and Transparency of Better Priced Orders, 89 FR 81620 (October 8, 2024): adoption on September 18, 2024; compliance dates; 2023 odd-lot rates and May 2020 odd-lot analysis
• Nasdaq Trader, UTP Vendor Alert #2025-10, Regulation NMS Mandated Round Lot Changes (May 7, 2025): effective November 3, 2025
• Nasdaq Trader, UTP Vendor Alert #2026-5, Dissemination of Odd-Lot Data (February 3, 2026): odd-lot quotes from April 27, 2026
• eCFR, 17 CFR 240.13e-4, Tender offers by issuers: odd-lot preference in (f)(3)(i)
• FINRA, Bonds: par value and percentage-of-par quotes
• TreasuryDirect, Treasury Notes: $100 minimum and increments
• MSRB Regulatory Notice 2016-13, Request for Comment on Draft Amendments to MSRB Rule G-15(f) on Minimum Denominations (April 7, 2016; filed as an exhibit with the SEC)
• FINRA, Trade Activity and Trade History Data: TRACE dissemination caps of $5 million and $1 million
• FINRA, Options: 100 shares per standard contract
• CFTC, How to Read Futures Price Tables: corn contract of 5,000 bushels
• CFTC, Commitments of Traders, CME futures only and Traders in Financial Futures, positions as of September 22, 2026: contract sizes
• OANDA, Micro lots (US help) and tastyfx, Forex product details
• eCFR, 17 CFR 5.9, Security deposits for retail forex transactions
• IRS, Publication 550, Investment Income and Expenses: identifying shares sold and FIFO default