Round lot, board lot and odd lot

Definition

A round lot (also called a board lot) is the standard number of shares an exchange sets as the normal trading unit. An odd lot is any quantity smaller than that unit.

The two names for the standard unit come from different markets. "Round lot" is common in US usage. "Board lot" is common in Asian and Commonwealth markets, where orders in the standard unit trade on the main board. Both answer the same question about lot size in stocks: what is the normal block of shares the main order book is built around?

Worked example (hypothetical)

Say an exchange sets the board lot for a share at N shares.

• An order for N shares, or for any whole multiple of N, is a round-lot order. It goes to the main order book and trades at the normal displayed prices.
• An order for fewer than N shares is an odd-lot order. Many exchanges send it to a separate odd-lot market or board, where there are fewer participants and the prices can differ from the main board.
• An order for a whole multiple of N plus a few extra shares is a mixed lot. Some systems split it into a round-lot part and an odd-lot part, which can fill at different prices or at different times.

The exact value of N and how odd lots are handled depend on each exchange's rules. Check the current rulebook of the exchange or ask your broker.

Where you see these terms

• Trading screens: a "lot size" or "market lot" field next to the symbol, and sometimes a separate odd-lot tab or board.
• Order tickets: a warning or rejection when the quantity is not a multiple of the board lot on the main board.
• Contract notes and account statements: odd-lot trades are often shown separately. See account statement.
• News and corporate notices: bonus issues, rights issues and share splits often leave holders with odd lots. Notices then explain how fractions or odd lots are settled.

In Pakistan, Securities and Exchange Commission of Pakistan (SECP), with trading in listed securities and commodities only via SECP-licensed securities and futures brokers. Per the SECP, lists of licensed brokers are on the PSX and PMEX websites.

Precise points and edge cases

• Price-dependent lots: some exchanges set the round lot by share price band. Expensive shares get a smaller standard unit and cheap shares a larger one. The lot size can therefore change when the price moves into another band.
• Quotes: on some markets, odd-lot orders are not counted in the displayed best bid and offer. The visible quote then does not show every order resting in the book.
• Liquidity: odd-lot boards are usually thinner. Fills can be slower or only partial. See fill and partial fill.
• Auctions: odd lots may be excluded from, or treated separately in, opening and closing auctions.
• Forex and CFDs are different: there, a "lot" is a contract size set by the broker. It is not an exchange board lot, and fractional lots are normal. Leveraged CFD and forex trading can lose money fast.

Related terms

• Contract size
• Free float
• Fill or kill and IOC
• Fat finger error
• Dealer
• Trading glossary
• Trading basics

Frequent questions

What is the board lot meaning in simple words?

It is the standard block of shares an exchange expects orders to use on its main board.

Is a round lot the same as a board lot?

Yes. Both terms mean the standard trading unit. The name depends on the market.

Can I buy an odd lot?

Many exchanges allow it, often through a separate odd-lot market. Check your exchange's rules and ask your broker how they handle these orders.

Why do I suddenly hold an odd lot?

Corporate actions such as bonus or rights issues, splits, or partial sales often leave quantities that are not a multiple of the board lot.

Is a forex lot the same thing?

No. A forex or CFD lot is a contract size defined by the broker, not an exchange trading unit.