What it means
When a trading day begins, the first completed trade or the result of an opening auction sets the opening price. It is the first official price of the day, and it is recorded alongside the high, low and closing prices in charts and data feeds.
For heavily traded shares the opening price appears within moments of the market opening. The opening price matters because it captures the market's reaction to everything that happened since the last close.
Company announcements, economic data and price moves in overseas markets all feed into it. A big difference between yesterday's close and today's open is called a gap, and it often signals a significant change in expectations.
Traders use the opening price as a reference point during the day. Whether the price is trading above or below the open is a quick measure of whether buyers or sellers have been in control.
Some investors also look at the relationship between the open and the close to judge the day's momentum. There is some nuance in how the price is determined.
Many exchanges use an opening auction, so the opening price may not be the same as the first trade on a screen, and it can differ between venues that trade the same security. Thinly traded shares may open late or at a price that is not very representative.
Corporate events often show up first in the opening price. Share issues, takeover bids and profit warnings announced outside trading hours are absorbed by the market in one step at the open, which makes the gap a handy measure of how investors judged the news.
For finance teams, the opening price is rarely used for valuation, since the closing price is normally the official reference for accounts and funds. It remains important for analysing share price reactions to events, such as an earnings release, and for understanding how a new listing begins trading.
In practice
Real-world examples.
Example
A retailer reports weak sales before the market opens. Its share price opens 6% below the previous close, and the investor relations team immediately prepares a statement to reassure shareholders.
Example
A trader compares the day's high with the opening price to see whether a stock rallied or faded during the session. She uses the pattern to judge whether to hold or sell a position overnight. A stock that opens high and fades all day can be a warning sign.
Example
A newly listed company sets an offer price of $20 per share. The shares open at $26 on the first day, and the finance director estimates how much additional money the company could have raised if the offer price had been higher. She raises the point with the bankers who set the price.
Formula
Calculation
Gap = opening price - previous closing price
Gap percentage = gap / previous closing price x 100
A share closes on Monday at $50. Positive news arrives overnight and the share opens on Tuesday at $52, so the gap = 52 - 50 = $2. The gap percentage = 2 / 50 x 100 = 4%. If the share instead opened at $48, the gap would be 48 - 50 = -$2, which is -4%, signalling a negative reaction. Comparing gaps over several days helps an analyst see whether the market is reacting calmly or nervously to news.Case study
Seen in the real world.
Aurora Biotech is a fictional company that announced trial results late one evening. The share price had closed at $40, and the finance team prepared for strong market interest.
The next morning, the shares opened at $34, a gap of -$6 or -15%, because investors took the news badly. The chief financial officer used the opening price and the early trading volume to judge how severe the reaction was and to decide when to brief major shareholders.
In this illustrative case the shares recovered to $37 by the close, so the opening price overstated the final reaction. The team learned that the open captures first impressions, and it should be read alongside the rest of the day's trading. They now wait until the close before drawing conclusions for the board.
Watch out
Common mistakes.
- Assuming the opening price equals the previous closing price, when news overnight often creates a gap.
- Using the opening price for valuation, when the closing price is usually the official reference.
- Treating the opening price as a reliable guide to the day's direction, when early trading is often volatile and may reverse.
Questions
People also ask.
How is the opening price decided?
On many exchanges it is set by an opening auction that matches the buy and sell orders collected before the market opens, and on others it is the first trade of the day.
Why does the opening price sometimes differ from the previous close?
Because news, earnings releases and moves in other markets arrive while the market is shut, and orders reflecting them are executed at the open.
Is the opening price the same on every exchange?
Not necessarily, because each venue has its own auction and trades, so the same security can have slightly different opening prices.
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