What’s the Chance the Market Closes Green After a Gap Up?

A gap up—when the market opens higher than the previous day’s close—often sparks optimism among traders. But how often does that early surge lead to a green close, where the market ends above yesterday’s close? We ran the numbers to find out for the S&P 500.

There is a 72% chance the market closes green after a gap up.

Our backtest examined gap-up days where the market opened at least 0.1% higher than the prior day’s close. The results are compelling: there’s a 72% chance the market closes green, meaning higher than the previous day’s close, and a 27% chance it closes lower.

This strong bullish tilt suggests gap ups often carry momentum through the day. Yet, that 27% chance of a reversal warns traders to stay vigilant—factors like profit-taking or unexpected news can derail the rally. A gap up may tilt the odds in your favor, but the market always keeps you guessing.