Volume, relative volume at time of day, and dollar volume

Start in plain English

Three numbers describe how actively a stock trades:

• Share volume: the number of shares traded in an interval. A 100-share trade adds 100 shares, not 200, even though it has a buyer and a seller.
• Dollar volume: the money that changed hands, the sum of price × shares over every trade.
• Relative volume (RVOL): volume in an interval divided by a baseline, usually an average of past volume for a comparable interval.

For small-cap day traders, relative volume is the usual first answer to "is anything unusual happening in this stock today?" A stock that normally trades 50,000 shares by 09:45 and has traded 1,000,000 is behaving differently from its own history.

The core idea: RVOL is a ratio, and its denominator decides what it means. At a given time of day, compare volume so far with volume by the same time on past days, counted under the same session rules. That comparison is called relative volume at time of day.

FennEdge's article Volume and relative volume: what are you comparing? shows the basic split between a same-time and a full-day baseline. This lesson adds the session question, the baseline choices and dollar volume.

Relative volume at 09:45, four ways

All volumes in this example are Illustrative. Tamsin Optics is fictional.

Tamsin Optics released news at 07:00 ET. By 09:45 it has traded:

• 1,800,000 shares in premarket (04:00–09:29);
• 1,200,000 shares in the regular session (09:30–09:45).

Over the previous 20 sessions, it averaged:

• 150,000 shares in premarket;
• 300,000 shares in the regular session by 09:45;
• 2,500,000 shares in a full regular session.

The 300,000 same-time baseline is built minute by minute, not from daily totals. For each of the 20 past sessions, add up regular-session volume from 09:30 to 09:45, then average the 20 totals. Three of those sessions, for example, had 240,000, 410,000 and 260,000 shares by 09:45. A tool that stores only daily volume cannot build this baseline, which is one reason some tools fall back on a full-day average.

Four ratios can all be called "RVOL":

The all-session numbers add premarket to the regular session on both sides: 1,800,000 + 1,200,000 = 3,000,000 today, and 150,000 + 300,000 = 450,000 on an average day. 3,000,000 ÷ 450,000 = 6.666…, or 6.67 rounded.

Read each one for the question it answers:

• 4.00: the regular session so far is four times as active as an average regular session by 09:45.
• 6.67: counting premarket on both sides, today is about 6.7 times as active as an average day by 09:45.
• 0.48: today's regular session has already traded 48% of an average full regular session. It does not mean the stock is quiet.
• 10.00: today's premarket and regular volume divided by a regular-session-only baseline. It compares different windows, so it overstates activity.

The same stock, at the same moment, can read as "half a normal day", "four times normal" or "ten times normal", depending only on the arithmetic behind the label.

The conclusion: 4.00 and 6.67 are both fair, because each compares like with like. 0.48 answers a different question, and 10.00 is simply a mismatch. When a screen shows one number labelled "RVOL", find out which numerator and denominator it uses before comparing it with another screen or another stock. A quick check: if a busy stock shows a ratio below 1 at 09:45, suspect a full-day denominator. The rest of this lesson covers why time of day matters so much, how to choose a baseline, what counts as volume, and how dollar volume differs from share volume.

Why time of day matters

Volume is not spread evenly across the day. Across US stocks, it tends to be heavier near the open and the close than at midday, a pattern documented in academic studies since the 1980s (for example Jain and Joh, 1988). For small caps with news, premarket can add a large share of the day's volume before 09:30. That uneven profile is why a full-day denominator misleads early in the session. At 09:45, even an unusually active stock has usually traded only part of its full-day volume, so a full-day ratio sits low. Later in the day the gap between the two methods narrows, and at the close a full-day ratio and a same-time ratio measure the same thing.

A simple Illustrative profile shows the effect. Suppose a stock's average regular session trades 15% of its volume by 09:45, 40% by 11:00 and 100% by 16:00. A day that runs at exactly twice its normal pace then shows a full-day ratio of 0.30 at 09:45, 0.80 at 11:00 and 2.00 at the close, while its same-time ratio reads 2.00 all day.

No FennEdge study measures the small-cap intraday volume profile yet. A study of volume and spread by time of day is planned, so this lesson gives no measured curve.

Choosing a baseline

Every RVOL has a baseline, and each choice changes the number:

• Lookback length. 10, 20 or 50 sessions. A short lookback reacts to recent changes; a long one is steadier but may include a different market.
• Average or median. One past news day with ten times normal volume can double a 20-day average. A median is less affected by that one day.
• Sessions. Premarket and after-hours included or not, on both sides.
• Today excluded. The baseline should not include the day being measured.
• Share-count changes. After a reverse split, past share volumes need adjusting. In a 1-for-10 reverse split, 5,000,000 old shares correspond to 500,000 new shares. An unadjusted baseline makes today look ten times quieter.
• Thin history. A recent listing, or a stock that rarely trades, may have a baseline near zero, which makes any ratio huge and meaningless.

Write the baseline down next to the number, for example "RVOL 4.00 (regular session to 09:45 vs. 20-session average, split-adjusted)".

What counts as volume

Under the consolidated-tape rules, volume counts more prints than the price statistics do. Odd lots, premarket and after-hours (Form T) trades, late reports and off-exchange trades all add to consolidated volume. Official open and close messages from a venue do not. (UTP specification version 4.1, September 2026; CTS specification version 2.11b, 2026-01-29; checked 2026-10-06. The conditions are covered in Time & Sales.)

So "day volume" at 10:00 on most screens already includes premarket volume, while the official high of day does not include premarket prices (High of day, low of day and VWAP). Some platforms let you show regular-session volume only. Check which one your screen uses before you compute a ratio.

Dollar volume

Dollar volume adds up price × shares for every trade. Many tools approximate it as share volume × a single price, such as the close or VWAP. With prices that move a lot during the day, the approximation can be noticeably off, so state which price you used.

Dollar volume makes stocks at different prices comparable. One million shares at $0.50 is $500,000; one million shares at $8.00 is $8,000,000. The glossary entry dollar volume gives the definition, and the scalping lesson Is it liquid enough to scalp? applies it to position size.

Gappers differ widely in dollar volume. Among the 671 stocks in FennEdge's Gapper HOD study that gapped up 20% or more at the regular-session open (2026-07-01 to 2026-10-02; FennEdge archive; as of 2026-10-02; see Small-cap gapper statistics (2026)), full-day dollar volume, approximated as share volume × close, had a median of $109.8M. The 10th percentile was $19.6M (68 of 671 below $20M), the 90th percentile $633.3M, about 32 times the 10th, and 13 of 671 traded less than $1M. These are FennEdge computations from the study data, not figures printed in the study, and they cover full days, not the minutes in which anyone traded.

Dollar volume is completed activity. It does not show how much size is available at the current quote; that is a question for the order book (How to read Level 2).

Volume and float

Volume is sometimes compared with float, the shares available for public trading. Volume above the float does not mean every share changed hands: the same shares can trade many times in a day. Float, and what "float rotation" can and cannot show, is the next lesson: Float for day traders.

Observe vs. infer

Tamsin Optics at 09:45 ET (fictional; all figures Illustrative):

Common mistakes

• Mixing sessions. Premarket in the numerator, regular session only in the denominator.
• Using a full-day denominator early in the day and reading the result as "quiet".
• Comparing RVOL across platforms without matching lookback, sessions and averaging method.
• Comparing share volume across prices. Use dollar volume to compare a $0.50 stock with an $8 stock.

Apply it in FennEdge

• Small Cap Volume charts the daily combined share volume of the most active small caps, after price and market-cap filters. It is a daily measure of how busy the small-cap market is, not an intraday curve. Full data needs Pro or Max; other visitors see an overview (as of 2026-10-06).
• The Scanner (paid: Plus, Pro, Max) can rank stocks by volume and filter by a volume range in shares. It has no RVOL field (as of 2026-10-06), so a ratio with your own baseline is something you compute yourself.
• The Top Gappers Calendar lists past gap days. Its volume filter uses full-day volume, which is only known after the close, so use it for historical review.

What this lesson does not claim

• It does not claim that high relative volume predicts the direction or size of a move.
• The dollar-volume figures describe one FennEdge sample of gappers from 2026-07-01 to 2026-10-02.
• RVOL definitions vary between tools; the four in this lesson are examples, not a standard.
• Tamsin Optics and its volumes are fictional.

Go deeper

• FennEdge first. Article: Volume and relative volume: what are you comparing?. Tool: Small Cap Volume.
• Liquidity for position size: Is it liquid enough to scalp? in the scalping course.
• In this course: High of day, low of day and VWAP; next, Float for day traders.

Exercises

Three exercises follow this lesson: a concept check (which prints count toward consolidated volume), a calculation (relative volume at time of day from a five-session baseline) and a scenario (a low RVOL reading at 09:45). Exercises, answers and progress are available after signing in.

Primary sources

• UTP Plan. UTP Data Feed Services Specification, Version 4.1 (September 2026): §3.14 sale condition matrix (volume column).
• CTA Plan. CTS Pillar Output Specification, Version 2.11b (2026-01-29): Sale Condition field.
• Jain, P. C. and Joh, G.-H. (1988). The Dependence between Hourly Prices and Trading Volume. Journal of Financial and Quantitative Analysis 23(3).
• FennEdge. What time do small-cap gappers hit high of day? (sample definition; data as of 2026-10-02).

Sources checked 2026-10-06. Tamsin Optics and all volumes, baselines and prices in this lesson are fictional and Illustrative; the dollar-volume figures are measured and cited with their sample. This lesson is education, not a recommendation to buy or sell any security. Past patterns do not indicate future results.