Trading term

What is Gap fill?

A gap fill is when price comes back to where it closed before a gap. If a stock closes at $100 and opens at $102, the gap fills when it trades back down to $100.

A gap opens when a stock starts the day at a different price from the previous close. It fills when price trades back to that close: down to it after a gap up, up to it after a gap down. Traders often say gaps always fill, and some bet on it by trading against the gap at the open.

Most gaps do fill, but mostly because most gaps are small. Price moves around during the day, so it often reaches a level close to the open. Big gaps, usually from real news like earnings, fill much less often.

For example

In a test of 20 large US stocks from 2010 to 2026, about 80% of gaps under 0.5% filled the same day, but only about 9% of gaps of 5% or more did.

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Why it matters to you

The previous close is a level worth watching after a gap. But a gap fill is a tendency, not a rule, and price went as far the other way almost as often as it filled.

⚠ Trusting the win rate

Betting against gaps wins most days, but the days a gap doesn't fill can be big losers. In our test the average trade made about 0.01% before costs.

Frequently asked questions

Do gaps always fill?

No. In our test most stock gaps filled within a year, but only about 9% of gaps of 5% or more filled the same day. Gap ups in a rising market often never fill.

What does filling the gap mean?

It means price has traded back to the previous day's close. After a gap up, the day's low reaches it. After a gap down, the day's high reaches it.

Read the full guide

Technical analysisDo Stock Gaps Always Fill? 78,000 Gaps Since 2010, TestedWe tested every gap in SPY, QQQ and 20 big stocks since 2010. 64% filled the same day, but only 9% of 5%+ gaps did. And does fading gaps pay?9 min read

Related terms

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