What are pre-market and after-hours trading sessions?

In addition to the regular market session, US stocks also trade during extended hours:

  • Pre-Market Session: 4:00 a.m. – 9:30 a.m. (ET)
  • Regular Session: 9:30 a.m. – 4:00 p.m. (ET)
  • After-Hours Session: 4:00 p.m. – 8:00 p.m. (ET)

How are pre-market and after-hours prices determined?

Unlike the regular market session, the US stock exchanges do not publish a single official price for extended hours trading. Instead:

  • Prices are updated based on the last completed trade during the pre-market or after-hours session.
  • High, low, and last prices in extended hours are calculated using these trades, following Nasdaq and NYSE guidelines.
  • Odd-lot transactions (trades for fewer than 100 shares, including fractional shares) do not impact the official high, low, or last prices.

Why might prices look different across brokers?

Different brokers may apply extended hours pricing rules in slightly different ways. As a result, the pre-market and after-hours prices you see can vary across platforms.

For the most accurate view of trading activity, you can review the detailed trade history of the security, focusing on the most recent “non-odd lot” transaction.