Reading a Stock Quote

The bid and ask are the live prices. To sell now you meet the bid; to buy now you take the ask. In a liquid stock the difference is trivial, but in a thin one the last price can sit nowhere near either side, and an order placed against it will fill somewhere you did not expect. The glossary entry for the spread explains what that gap costs across a year of trading.

There is a second, quieter version of the same error. The change figure is calculated against the previous official close, which is set at the closing auction. If the stock traded heavily after hours, today’s open can sit well away from that close, and the percentage change on the quote will include a move that happened while the market was shut. A stock showing +1.36% may have opened up 1.30% and done almost nothing since.

Delayed data and the fifteen-minute trap

Many free quote sources publish exchange data on a delay, commonly fifteen minutes, because real-time data carries exchange fees. On a quiet day in a large stock the difference is cosmetic. Around an earnings release, a halt, or the opening minutes, fifteen minutes is an eternity, and acting on a delayed quote means acting on a price that no longer exists.

Two checks take seconds. Look for a timestamp and a real-time or delayed label on the quote itself. And compare the source you are reading against your broker’s own quote before placing anything; your broker’s is the one your order will meet.

The fields most people skip

• Bid and ask size. A four-cent spread with only 100 shares on each side is not liquidity, it is a narrow quote on an empty book. Size is what tells you whether the spread is real.
• Average volume. This is the field that decides whether your intended position is sensible. A $40,000 order in a stock trading 90,000 shares a day is a large fraction of the register’s daily activity.
• Previous close versus today’s open. A gap between them means the move happened outside the session, where you could not have acted on it.
• Currency and listing. The same company can be quoted in several places in different currencies, and a depositary receipt is not always priced in step with the home listing.

Turning a quote into a decision

A quote describes conditions, it does not contain a verdict. Nothing in those fields says whether the company is worth owning, which is the work done by earnings, cash flow and valuation.

What a quote does tell you is whether this is a sensible moment and size to transact: how wide the spread is, how much depth is behind it, how far price travels on an ordinary day, and therefore how much room a stop needs. Those four readings feed straight into the position size calculator, and the reasoning behind them is set out in the risk management guide.