Round lot / odd lot
Definition · Level 0 · Market basics
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The standard trading unit: 100 shares for most US stocks (since late 2025, 40, 10 or 1 share for stocks above $250, $1,000 or $10,000) / any quantity below that unit. 250 shares of a $50 stock = two of the first + a 50-share piece of the second.
Example
Where quote size is shown in 100-share units, “size 5” means 500 shares.
Rules and market figures change: check the current ones before relying on this.
Where Tradecraft teaches it
Level 0 · Market basics, in the lesson “Long, short & P&L”: Position direction, how profit and loss are measured, and the units traders quote them in.
Related terms
- Basis point (bp)One hundredth of one percent: 0.01% = 0.0001.
- Long positionOwning an asset, or a contract that gains as it rises: you profit when the price goes up.
- Mark-to-marketRevaluing open positions at current prices (typically each day’s close), so paper gains and losses flow into account equity and margin daily.
- P&LProfit and loss: the dollars a trade, position or whole book has made or lost over a period, the number every trader is judged on.
- PortfolioThe whole collection of positions an investor or fund holds, judged together for overall risk and return rather than one holding at a time.
- Realized vs unrealized P&LProfit or loss locked in by closing a position, versus paper profit or loss on a position still open, revalued at the current price.