Gap Up and Gap Down

"Tags: gap up, gap down, overnight risk, opening price, gap fill Prerequisites: Understanding Price, Volatility A gap is the market admitting that the previous closing price is no longer where buyers and sellers agree. Questions this article answers What creates an opening gap? Why does a stock skip prices between sessions? Do all gaps get filled? How do gaps affect stop-loss execution? 1. Definition A gap up occurs when a stock opens meaningfully above the previous session's closing area. A gap down occurs when it opens meaningfully below it. On a chart, an empty space may appear between the prior session and the new session, depending on the size of the move and the chart style. 2. Why prices can skip The market closes for many hours, but information and decisions continue. Results, announcements, global markets, policy events, commodity moves or unexpected news can change the price at which participants are willing to trade before the next session begins. When the exchange reopens, the first transaction may occur far from the previous close. 3. Pre-open price discovery Exchanges may use a pre-open process for eligible securities to collect orders and discover an opening price. The opening price reflects available demand and supply, not a smooth continuation from the previous close. 4. Gap size should be measured in percentage terms A Rs 20 gap is large in a Rs 200 stock but small in a Rs 4,000 stock. Percentage measurement makes comparison more meaningful. Gap % = (Opening Price - Previous Close) / Previous Close x 100 5. A gap is not automatically bullish or bearish A gap up can attract profit-taking and fail. A gap down can reverse strongly if selling is absorbed. The quality of the gap depends on location, volume, broader market context and price behaviour after the open. 6. Common descriptive gap types Traders often describe gaps as common, breakaway, continuation or exhaustion gaps. These labels are interpretations made after considering context. A beginner should not force a label immediately at the open. First observe whether price holds, extends, reverses or trades back through the gap. 7. The gap-fill myth A gap is considered filled when price later trades back through the skipped area, depending on the definition used. Many gaps eventually fill, but there is no rule that every gap must fill quickly or at all. Trading solely because a gap has to fill is a prediction, not a risk-controlled process. 8. Gap risk and stop losses Suppose a stock closes at Rs 500 and your stop is Rs 480. Bad news causes the next opening trade near Rs 430. A stop order may activate, but the actual execution can occur near the available market price, producing a loss much larger than planned. This is gap risk. 9. Position sizing for overnight risk No formula can eliminate surprise gaps. Liquidity, company-event risk, portfolio concentration and position size determine how damaging a gap can be. Holding multiple correlated positions can create simultaneous gaps during market-wide stress. 10. Results and event risk Scheduled events such as earnings announcements can cause large overnight re-pricing. A trader should know whether a major event is expected while a position is open and decide according to the system's rules rather than reacting after the gap. 11. Common beginner mistakes Buying every gap up Some gaps are late-stage excitement or immediate exhaustion. Shorting every gap up because it looks expensive Strong institutional repricing can continue. Assuming every gap fills There is no guaranteed timetable or outcome. Believing the stop price is guaranteed The first available execution may be far away. Ignoring portfolio-wide gap exposure Several holdings can gap together during systemic news. 12. DStreet principle Overnight uncertainty cannot be controlled. Exposure to it can be controlled. 13. Beginner checklist I measure gaps in percentage terms. I wait for price behaviour before assigning a gap label. I do not assume every gap must fill. I understand that stop execution can be worse than the stop price. I account for scheduled and unscheduled overnight risk. 14. Quick knowledge check Question: What is a gap up? Answer: An opening meaningfully above the previous closing area. Question: Why can price skip overnight? Answer: Participants change their acceptable prices while the market is closed. Question: Do all gaps fill? Answer: No. Question: Can a stop prevent gap loss? Answer: It can trigger an exit but cannot guarantee the stop price. 15. Next lesson Upper and Lower Circuits explains exchange price bands and why a visible exit order may remain unexecuted."