Relative Volume (RVOL)

Relative volume (RVOL) is current volume divided by the stock's average volume for the same point in the session; a reading of 3.0 means the stock has already traded three times its normal share count for that time of day. It is the standard screen for whether anything unusual is happening in a name.

The time-of-day adjustment is the whole point. Volume is front-loaded: a typical stock does a large share of its daily volume in the first hour, so comparing 10:00 am volume against a full-day average understates the signal. Momentum traders generally want RVOL of at least 2, and the gappers that sustain big intraday moves often carry RVOL of 5-10 or more.