In a stock quote, “bid x size” shows two numbers separated by an “x”: the bid is the highest price a buyer is currently willing to pay for the stock, and the size is the number of shares available at that price. So a quote reading “150.25 x 500” means buyers collectively want 500 shares at $150.25 each. As of November 2025, U.S. equity exchanges display size in actual shares, not in round-lot multiples, so the number on your screen is the share count with no multiplication needed.
Reading the Two Numbers
The “x” is just a separator. The dollar figure on the left is the bid price. The whole number on the right is how many shares buyers want at that price combined across everyone bidding. If you sold at market right now, the bid is the best price you would get, and the size is how many of your shares would fill at that price before the order moves to the next-best bid.
The bid you see on most brokerage screens is the National Best Bid, the highest bid across all U.S. exchanges. Securities Information Processors consolidate quotes from every exchange in real time and give priority first to the highest price, then to the largest size at that price, and finally to the earliest timestamp.1CTA Plan. CQS Participant Input Binary Specification
The Full Quote: Bid, Ask, and the Spread
A complete quote shows both sides, usually written like “85.10 x 300 / 85.15 x 200.” The left side is the bid. The right side is the ask, which is the lowest price any seller is currently willing to accept.2Investor.gov. Ask Price The gap between them is the spread, and it works as a built-in transaction cost. Buy at the ask and immediately sell at the bid, and the spread is what you lose.
The sizes on each side add context. If the bid size is much larger than the ask size, buying interest outweighs selling interest at those price levels. Neither number alone tells the full story, but comparing them gives a quick read on where the weight of the market sits.
What the Size Number Represents Today
For most of stock market history, a round lot meant 100 shares, and quote sizes were displayed in round-lot multiples: a “5” on the screen actually meant 500 shares. Orders smaller than 100 shares (odd lots) generally didn’t appear in the displayed quote or contribute to the National Best Bid and Offer.3Federal Register. Self-Regulatory Organizations: Investors Exchange LLC Notice of Filing
That changed on November 3, 2025. Under amended Regulation NMS, exchanges now display size in actual shares, and the round-lot threshold varies with a stock’s average closing price:4U.S. Securities and Exchange Commission. Final Rule – Regulation NMS: Minimum Pricing Increments, Access Fees, and Transparency of Better Priced Orders
- $250.00 or less per share: 100 shares
- $250.01 to $1,000.00: 40 shares
- $1,000.01 to $10,000.00: 10 shares
- $10,000.01 or more: 1 share
The displayed size is rounded down to the nearest multiple of the applicable round lot. For a $600 stock with a round lot of 40 shares, total buying interest of 117 shares would display as 80.1CTA Plan. CQS Participant Input Binary Specification Orders smaller than the applicable round lot are still odd lots and don’t contribute to the protected NBBO quote, though they can still execute.3Federal Register. Self-Regulatory Organizations: Investors Exchange LLC Notice of Filing
The practical effect for a reader interpreting a quote: a size of 500 means 500 shares. No multiplier. And for higher-priced stocks, smaller orders now count toward the national quote than they used to.5U.S. Securities and Exchange Commission. Notice of Filing and Immediate Effectiveness of a Proposed Rule Change
What Bid Size Tells You About Depth
A large bid size at a price level acts as a cushion against selling pressure. If 10,000 shares are stacked at $85.10, a 500-share sell order barely dents that wall of demand. Traders often call these concentrations support levels because the price has to work through all that buying interest before it can fall further.
A thin bid size signals the opposite. If only 100 shares sit at the best bid, one modest sell order clears it out and the next-best bid may be several cents lower. That’s where bid size stops being abstract and starts costing money, especially for anyone trying to exit a position quickly.
One caveat matters. A large displayed bid size doesn’t guarantee the price will hold. Those orders can be canceled at any moment, and some high-frequency strategies involve placing large visible orders that get pulled milliseconds before they’d fill. The bid size is a snapshot of stated intent, not a binding commitment.
When Your Order Is Bigger Than the Size
If you place a market sell order for 1,000 shares but the best bid only shows 300, the order doesn’t stop at 300. The exchange’s matching engine fills 300 shares at the best bid, then moves to the next-best bid (which is lower), fills more shares there, and keeps walking down the order book until the full 1,000 shares are done. Your average sale price ends up lower than the quoted bid.
That price deterioration is called slippage, and checking the bid size before placing large orders is how experienced traders anticipate it. On a liquid stock with deep bids at every penny, slippage on a 1,000-share order might be negligible. On a thinly traded stock, it can eat a real chunk of your expected proceeds.
A limit order avoids this by refusing to execute below your specified price, but you trade certainty of fill for certainty of price. If the market moves away, the order sits unfilled. Breaking a large order into smaller pieces over time is another common way to reduce slippage.
What the Displayed Size Doesn’t Show
The bid size on your screen understates total buying interest, sometimes by a lot. Two sources of hidden liquidity account for most of the gap.
Iceberg orders (also called reserve orders) let a trader display only a fraction of their total order. A buyer who wants 10,000 shares might show only 200 at a time. Each time the visible portion fills, another 200 shares automatically appear at the same price. The hidden portion doesn’t get priority at that price level, so other visible orders at the same price fill first, but the total buying interest behind that bid is far larger than what shows on the screen.
Dark pools are private trading venues that don’t display orders on public exchanges at all. They handle a meaningful percentage of U.S. equity volume. Every share matched in a dark pool is a share that never appears in a displayed bid or ask size, so the quote reflects only the “lit” market, not the full universe of interested buyers.
Options Quotes Use the Same Format, but Size Means Contracts
Options quotes are written the same way, but the size number means something different. In options markets, size is the number of contracts, not individual shares. Each standard equity option contract covers 100 shares of the underlying stock, so a bid size of 10 represents 10 contracts, or the equivalent of 1,000 shares.
The dollar math changes too. An option bid of $3.50 with a size of 10 is 10 contracts at $3.50 per share times 100 shares per contract, or $3,500 in total premium. When comparing liquidity between a stock and its options, the raw size number is misleading unless you account for the contract multiplier.