What can you learn from Market Depth before the market opens?

Before the market opens at 10 a.m., the period from 7 a.m. until the opening is known as the Pre-Open. During the Pre-Open, you can place trades in anticipation of the market opening at 10 a.m.

Key Pre-Open Timings


7:00 AM – 09:59 AM AEST:

  • The market is in pre-open.
  • Traders can place, amend, or cancel orders.
  • Orders are visible in the order book.

Indicative Opening Prices (IOP) are published, showing where the stock may open based on current orders.

09:59 – 10.00 AM AEST:

  • The system randomly triggers the opening auction.
  • Buy and sell orders are matched at a single equilibrium price where the most shares can trade.
  • An Opening Price is set.


10:00 AM AEST:

  • Official trading then begins in the continuous market phase.

How the Pre-Open Auction Works

  1. Orders are entered: Traders input “at limit” or “at market” buy and sell orders.

  2. Indicative prices update: The ASX calculates an Indicative Opening Price based on order book supply and demand.

  3. No trades have happened yet: Orders are visible, but no matching or trading occurs until the opening match.

  4. At the auction (10:00 AM):

  • The ASX matches the most buy and sell orders at one single price point.
  • This becomes the official opening price for each stock.

Equilibrium Price

The Equilibrium Price is only available before the market opens, and it is the point at which the bid and ask orders match at a particular price.

This is the Indicative Match Price before the market opens, and the match occurs.

The Equilibrium Price serves as a reference point guiding future transaction pricing.

It evaluates asset valuation before trading, signaling whether it’s overvalued, undervalued, or appropriately priced.

Auction and Surplus Volume

Auction Volume is the volume traded at the auction match price.

Surplus Volume is the imbalance volume of orders included in the market match, showing the surplus amount difference between the bid and ask.

Count and Quantity

The Count refers to the number of orders at that price point.

The Quantity is the total volume of the orders at that price point.

If the Bid has a Quantity of 3,931, it comprises the total of 3 orders in the Count.

How much is traded on the opening session, 10.00 – 10.30 AM?

  • Trading Volume: Approximately 15–20% of total daily activity occurs during the opening thirty minutes.
  • Price Movement: Market open typically exhibits peak volatility as traders react to overnight international developments, corporate announcements, and global market shifts.
  • This period features price gaps, expanded spreads, and sharp directional movements as the market establishes initial price discovery.

The Bottom Line

Market depth before the market opens strongly indicates the price direction of the stock before trading begins.

Understanding:

  • The Equilibrium price indicates the price at which bids and asks will match.
  • Which side has higher volume: bids or asks?
  • The number of orders at each price step can indicate strength.

  • How to find where the market depth?

    Read More

You can download the offline guide here Understanding Market Depth Before The Open

What you learn here has been used in our Trade for Good software.
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