Relative volume (RVOL)
Also called: RVOL, relative volume, volume ratio
Today's trading volume divided by the stock's typical volume for the same period, so a reading of 3.0 means three times the usual activity.
Last verified
How it is calculated
RVOL = Volume in the current period ÷ Average volume for the same period over a baseline window
The baseline is usually an average over a recent window, such as 30 trading days. The key choice is which period is being compared. Comparing a full day with a full day is straightforward. Intraday, a fair comparison uses the same time window: volume traded by 10:00 ET today against the average volume traded by 10:00 ET on past days, or premarket volume against past premarket volume.
Worked example
Hypothetical: Company X normally trades 40,000 shares in the premarket session (04:00 to 09:30 ET), averaged over the last 30 sessions. This morning it has traded 360,000 shares by 09:30. Premarket RVOL is 360,000 ÷ 40,000 = 9.0.
Comparing the same 360,000 shares with its average full-day volume of 1,200,000 would give 0.3, which compares a partial session with a whole day and understates how unusual the morning is.
Why it matters
RVOL flags when a stock is trading far more than usual, which often coincides with news, a filing, an offering or a halt. It puts raw volume in context: 500,000 shares is ordinary for one stock and extraordinary for another.
Limits of the measure
- Thin baselines. If a stock barely trades at a given time of day, a small amount of volume can produce a very large RVOL.
- New listings. A stock with little trading history has no meaningful baseline, so RVOL is not measured rather than zero or infinite.
- Splits. Reverse splits change share counts, so volume before and after a split should be compared on the same basis.
How to spot it
The Signal8 premarket screener shows RVOL for premarket movers. See Premarket RVOL.
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