Do Stock Gaps Always Fill? 78,000 Gaps Since 2010, Tested
"Gaps always fill" is one of the oldest sayings in trading. We checked 78,735 gaps in SPY, QQQ and 20 large US stocks, then tested the trade most people build on it: betting against the gap at the open.
By Pavel Penev, MScFounder, TradeWize · 10+ years trading the marketsA gap is when a stock opens at a different price from where it closed the day before. If it closed at $100 and opens at $102, that's a 2% gap up.
Traders say gaps "always fill". That means price comes back to the previous close sooner or later. Some people trade on it: they bet against the gap at the open and wait for it to close. So we tested both the saying and the trade, on every trading day from January 2010 to November 2026.
The short answer
Most gaps fill, but not because they're gaps. 64% of stock gaps filled the same day, and 97% within a year. But price went the same distance the other way almost as often, 61% of the time. Small gaps fill because they're small. Big ones mostly don't: only 9% of gaps of 5% or more filled the same day. Betting against gaps won most days and made almost nothing.
What this article is, and isn't
This is a test with public data, not personal financial advice, and there are no affiliate links on this page. The prices are Yahoo Finance's daily prices, linked at the end. Day trading is high risk, and most people who try it lose money.
What "filling the gap" means
Say a stock closes at $100 and opens the next morning at $102. The gap is the $2 between the two prices. It fills when price trades back down to $100. For a gap down it's the same in reverse: the gap fills when price climbs back to the previous close.
Most gaps come from news while the market is shut, like earnings or something that happened overnight. Some are just the market drifting in the hours before the open.
How we tested it
We took daily prices for SPY (the S&P 500 fund), QQQ (the Nasdaq 100 fund) and 20 of the biggest US stocks: AAPL, MSFT, AMZN, NVDA, GOOGL, META, TSLA, JPM, XOM, JNJ, WMT, KO, PG, INTC, CSCO, BAC, DIS, NFLX, AMD, BA. The window runs from 4 January 2010 to 11 November 2026.
A gap is any open at least 0.1% away from the previous close. That gave 3,407 gaps in SPY, 3,553 in QQQ and 71,775 across the stocks. Gaps are everywhere: SPY opened with one on 80% of trading days.
On the day a stock pays a dividend, its price drops by the payout at the open. We took that out, so a dividend doesn't count as a gap down.
How often gaps fill
Most gaps fill, and most of those fill fast. In SPY, 56% filled the same day, 81% within 5 trading days and 97% within a year. The stocks filled a bit more often: 64% the same day and 97% within a year.
| Gap size | Gaps | Same day | Within 5 days | Within 20 days | Within a year |
|---|---|---|---|---|---|
| 0.1% to 0.5% | 34,884 | 80% | 92% | 96% | 99% |
| 0.5% to 1% | 19,516 | 59% | 83% | 91% | 98% |
| 1% to 2% | 11,809 | 42% | 74% | 86% | 96% |
| 2% to 5% | 4,620 | 28% | 62% | 77% | 92% |
| 5% or more | 946 | 9% | 33% | 52% | 80% |
20 large US stocks. "Within a year" counts only gaps with at least a year of prices after them.
Size changes everything. A gap under 0.5% filled the same day 80% of the time. A gap of 5% or more filled the same day only 9% of the time, and only 52% filled within a month (20 trading days). A big gap is usually real news, and the market doesn't take it back.
It varied from stock to stock, but not by much. NFLX filled 71% of its gaps the same day and XOM 58%. TSLA had the most big gaps: 141 of 5% or more.
Gaps fill because they're close, not because they're gaps
Here's the catch. A stock moves around a lot in a day. If it opens 0.3% above yesterday's close, there's a good chance it touches that close at some point just by wiggling.
So we ran a control. On every gap day we also checked whether price went the same distance the other way. For that $102 open after a $100 close, did it reach $104 that day? If gaps really "want" to fill, the fill should happen far more often than that.
Every gap of 0.1% or more in 20 large US stocks, 4 January 2010 to 11 November 2026.
It barely does. Across the stocks, 63.6% of gaps filled the same day, and 61.2% went as far the other way. In SPY it was 55.8% against 49.1%, and in QQQ 56.8% against 51.8%.
So there's a small pull back toward the previous close, a few percentage points. Most of the high fill rate is just distance. Small gaps are close to the old price, so price gets there. Big gaps are far away, so it usually doesn't.
Learn it by doing
Reading about it is one thing — it clicks when you do it. Learn it hands-on with free, interactive lessons on TradeWize.
Try the free lesson →The gaps that never fill are gap ups
Over the long run, gap downs almost always filled. Of SPY's gap downs with a year of prices after them, 99.8% filled within that year, and none is still open today. Gap ups were different: 73 SPY gap ups more than a year old have never filled.
That's not about gaps either. Stocks have mostly gone up since 2010. A gap down sits above the price, and a rising market climbs back through it. A gap up sits below, and a rising market can leave it behind for good.
The oldest one in our data is from 7 July 2010. SPY closed at $102.87 the day before and opened at $103.13. The lowest it traded that day was $103.02, 15 cents short. It has never been that low since. SPY last closed at $759.81.
Across the 20 stocks it's the same picture: 1,087 gap ups over a year old are still open, against 28 gap downs.
Does trading the gap fill make money?
The usual gap-fill trade is a fade. You bet against the gap at the open: sell short after a gap up, buy after a gap down. You put a limit order at the previous close to take profit if the gap fills. If it doesn't, you close at the end of the day. We tested it with no stop-loss, on every gap.
| Market | Trades | Won | Average win | Average loss | Average trade |
|---|---|---|---|---|---|
| SPY | 3,407 | 66% | 0.39% | −0.61% | 0.05% |
| QQQ | 3,553 | 65% | 0.44% | −0.84% | −0.00% |
| 20 stocks | 71,775 | 71% | 0.58% | −1.37% | 0.01% |
Before costs. A trade is measured from the open to the fill or the close.
It wins a lot. Across the stocks, 71% of trades made money. But the losers were about 2.3 times bigger than the winners. When a gap doesn't fill, the stock often keeps running all day.
Put together, the average stock trade made 0.01%. That's about $1.21 on $10,000, before you pay the spread to get in and out. On QQQ the average trade lost money. A high win rate says nothing on its own. What matters is the average trade.
It worked better on gap downs than gap ups, because the market's long climb helped the buys. On SPY, buying gap downs made 0.09% a trade and shorting gap ups made 0.01%. On the stocks, shorting gap ups lost 0.02% a trade.
On SPY, it made a little
SPY did best, at 0.05% a trade. SPY's spread is tiny too: one cent is about 0.13 basis points (bp), where 1 bp is 0.01%. So we ran $10,000 through every SPY gap and compared it with just holding SPY.
| Strategy | Worth at the end | A year |
|---|---|---|
| Fade, no costs | $43,968 | +9.2% |
| Fade, 0.5 bp a trade | $37,084 | +8.1% |
| Fade, 1 bp a trade | $31,277 | +7.0% |
| Fade, 2 bp a trade | $22,249 | +4.9% |
| Fade, 3 bp a trade | $15,826 | +2.8% |
| SPY, held | $91,585 | +14.0% |
SPY held includes its dividends. The fade is only in the market during the day, so it earns no dividends.
Month-end values, 4 January 2010 to 11 November 2026. Log scale, so equal gaps are equal percentage gaps.
With no costs, $10,000 became $43,968, about 9.2% a year. Holding SPY turned it into $91,585. At 1 bp a trade, the fade ended at $31,277. It stops making money at about 4.3 bp a trade.
The fade was much calmer. Its worst fall was 12.6%, against 33.7% for SPY. But it trailed SPY in 11 of 17 years, and one year did a lot of the work: in 2020 it made +36.2%, when the market swung hard both ways.
And the same rule on QQQ, a fund that tracks the stocks most people actually trade, made nothing. One fund working and its closest cousin not working is a warning sign. It's what you'd expect if the SPY result is partly luck.
What this test can't tell you
- We used daily prices. They tell us whether price reached the previous close during the day, but not when. A fade that fills at 3:55 pm is a long, stressful day.
- We assumed you get the official opening price. In real trading, a market order at the open can fill a little worse, especially on a fast gap.
- Shorting needs a margin account, and costs to borrow. We left that out.
- The 20 stocks are big, well-known companies that are still around today. Smaller stocks gap more and are dearer to trade.
- We tested only the regular session. Prices that moved before the open, in pre-market trading, aren't counted.
So do gaps always fill?
No. Most do, but mostly because most gaps are small. 80% of stock gaps under 0.5% filled the same day. Only 9% of those of 5% or more did. And price went just as far the other way almost as often as it filled.
The ones that stay open are gap ups in a rising market. If you trade the fill, expect to win most days and still make very little. On 20 big stocks it made 0.01% a trade before costs, which a normal spread wipes out. Treat a gap edge as a level worth watching, like any other support or resistance, not as a promise.
Do stock gaps always fill?
No. In our test of 20 large US stocks since 2010, 64% of gaps filled the same day and 97% within a year. Gaps of 5% or more filled the same day only 9% of the time.
What percentage of gaps fill the same day?
About 64% for large stocks and 56% for SPY. It depends on size: 80% of stock gaps under 0.5% filled the same day, against 9% of gaps of 5% or more.
Do gap ups or gap downs fill more often?
Over the long run, gap downs. Of SPY's gap downs with a year of data after them, 99.8% filled within a year. 73 gap ups more than a year old never filled, because the market kept rising.
Is trading the gap fill profitable?
Barely. Betting against every gap at the open won 71% of trades on large stocks but averaged 0.01% a trade before costs. On SPY it made 0.05% a trade, but still trailed just holding SPY.
Why do gaps fill?
Mostly because they're small. A stock moves around during the day, so it often touches a price that's close to the open. In our test, price went the same distance away from the fill almost as often as it filled: 61% against 64%.
Learn to read levels on a chart
Our technical analysis track teaches support, resistance, breakouts and stops with drills on real-looking charts.