What it means
Quotes are usually shown as a pair, for example $24.90 by $25.00. The first number is the bid, so $24.90 is what you would receive if you sold immediately; the second is the ask, so $25.00 is what you would pay to buy immediately.
The ask is sometimes called the offer, and the two words mean the same thing in practice. The reason the two prices differ is that someone has to stand ready to trade on both sides, and that market maker earns the spread as compensation for holding inventory and taking on risk.
A heavily traded large-cap share might have a spread of one cent, while a thinly traded small company, a corporate bond or an unusual option contract can trade with a spread of several per cent. The size of the spread is a direct measure of liquidity and a real, if invisible, cost of trading.
Buying at the ask and selling at the bid means the position starts underwater by the full spread, which is why frequent trading in illiquid instruments erodes returns even when every individual decision looks sensible. Ask sizes matter as much as ask prices.
A quote of $25.00 for 200 shares tells you nothing useful if you want 20,000, because filling that order will walk up through higher asks in the order book and produce an average price above the headline quote. Traders who do not want to pay the spread place a limit order at or near the bid and wait, accepting the risk that the trade never fills.
Institutions do the same thing at scale, slicing large orders into small pieces so their own buying does not push the ask away from them.
In practice
Real-world examples.
Example
A finance manager buying $2m of a widely held index fund sees a one cent spread on a $50 price, a cost of roughly 0.02%, and executes at market without a second thought.
Example
A family office buying a small-cap share quoted $18.20 bid, $18.95 ask works out that crossing the 4% spread would cost about $40,000 on a $1m order. They place a limit order at $18.45 and fill it over three days instead.
Example
A treasury team selling a corporate bond gets three dealer quotes with asks of $98.40, $98.75 and $99.10 per $100 of face value. The dispersion tells them the bond is illiquid, so they negotiate rather than hitting the first price offered.
Formula
Calculation
Bid-ask spread = Ask price - Bid price
Spread percentage = (Ask - Bid) / Midpoint, where Midpoint = (Ask + Bid) / 2
Suppose a share is quoted $24.90 bid, $25.00 ask. The spread is $25.00 - $24.90 = $0.10, and the midpoint is ($25.00 + $24.90) / 2 = $24.95, so the spread percentage is $0.10 / $24.95 = 0.40%. Now assume an investor buys 10,000 shares at the ask and immediately sells them at the bid. The purchase costs 10,000 x $25.00 = $250,000 and the sale returns 10,000 x $24.90 = $249,000, so the round trip loses $250,000 - $249,000 = $1,000 before any commission. Measured against the midpoint, the cost of demanding immediacy on the buy alone is 10,000 x $0.05 = $500.Case study
Seen in the real world.
Ridgeforth Capital is a fictional boutique investment firm used here as an illustrative case. Its analysts were confident in a thinly traded industrial supplier quoted at $24.90 bid, $25.00 ask, and put in an order for 40,000 shares at market on a quiet Tuesday morning. Only 3,000 shares were available at $25.00.
The rest of the order climbed the book, filling at $25.15, $25.40 and eventually $25.85, for an average price of about $25.38. That was $0.38 above the quoted ask, or roughly $15,000 of extra cost on a $1m position, and it happened because the firm read the ask price without checking the ask size.
The illustrative lesson stuck. Ridgeforth changed its process so that any order larger than 20% of the average daily volume is worked as limit orders over several sessions, and its measured slippage on small-cap trades fell by more than half the following quarter.
Watch out
Common mistakes.
- Reading the ask as the market value of a holding. Portfolios are normally marked at the bid or the midpoint, because the ask is what you would pay to buy, not what you would receive to sell.
- Ignoring the ask size behind the price. A tight quote for 100 shares says nothing about the cost of buying 50,000.
- Treating commission as the only trading cost. In illiquid instruments the spread usually costs several times more than the broker's fee.
Questions
People also ask.
Is the ask the same as the offer?
Yes, the two terms are used interchangeably for the lowest price at which someone will currently sell.
Why is the ask always above the bid?
Because market makers earn the difference for standing ready to trade on both sides and carrying the inventory risk in between.
How can I avoid paying the ask?
Use a limit order at or below the current ask and wait for a seller to come to your price, accepting that the order may not fill at all.
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