Pre-Market Gaps: How Gap-Ups Work and What to Watch

A gap is when a stock trades well above (gap up) or below (gap down) its previous close, leaving a "gap" on the chart. Most gaps form in the pre-market session, from 4:00 AM to 9:30 AM ET.

What causes gaps

• Earnings reports released after the close or before the open.
• Company news: contracts, trial results, approvals, mergers and offerings.
• Sector or market-wide news overnight.

Measuring a gap

Gap % = (current price − previous close) ÷ previous close × 100

A stock that closed at $4.00 and trades at $5.00 pre-market has gapped up 25%. Traders also watch the pre-market high and low and pre-market volume: a gap on heavy volume shows more interest than one on a few thousand shares.

Pre-market trading is different

Fewer people trade before the open, so spreads are wider and prices can jump around. A pre-market price can change a lot by 9:30 AM.

Gaps don't always hold

Some gaps keep running after the open; many fade, and some "fill" (the price falls back to the previous close). A gap is a starting point for research, not a prediction.

How Nexus Screener shows it

• The Morning Brief lists pre-market gappers from 4:00 AM ET, biggest gap first, with pre-market volume, high, low and float.
• The "Up 10% Today" scan and news flags on every card show what's moving and why.
• Charts mark the pre-market high and low.