Volume Z-Score Indicator: Formula, Settings and How to Read It
Volume Z-Score expresses a bar's volume as the number of standard deviations it sits away from the mean volume of the bars before it. With the default period of 20, a reading of 2 means the bar traded two standard deviations above the average of the twenty preceding bars.
Senzoukria · Indicators · Updated September 2026
Volume Z-Score ships with the Senzoukria desktop app, in the Tape & flow group of the indicator catalogue. It is drawn in its own panel below the chart.
What Volume Z-Score measures
The mean and the standard deviation are computed over the bars strictly preceding the current one, using the population formula, so a large bar never inflates its own reference and never damps its own reading. Two cases return no value rather than a number: a bar that does not yet have a full window behind it, and a window in which volume is perfectly constant, where the standard deviation is zero and the ratio is undefined. The default period of 20 is the usual reference for judging whether a bar's volume is unusual against its recent history.
The formula, as implemented
This is not a description of how the indicator is usually defined elsewhere — it is what the shipped code computes, documented next to the implementation:
Z-score du volume : (vol[i] − μ) / σ où μ/σ (population, ÷N) portent sur les N barres STRICTEMENT précédentes (fenêtre [i−N, i−1] — convention de famille, cf. en-tête : la barre courante ne dilue pas sa référence). Warm-up (< N barres avant i) ou σ = 0 (volume constant : z indéfini) → null. Défaut N=20, la référence usuelle du volume « anormal ».
How to read it
- Readings around zero describe a bar whose volume is ordinary for the recent context.
- Negative readings mark bars quieter than the recent average, and a run of them marks a stretch of low participation.
- A high reading says the bar is unusual against its own recent history, not against the day, the instrument or the same hour on other days.
- Because the current bar is excluded from its reference, a spike reads at full size when it prints; once it enters the window it raises both the mean and the dispersion, so an equally large bar a few bars later reads lower.
- Keep the raw volume pane nearby: the z-score tells you how unusual a bar is, never how much traded.
Parameters and defaults
Period defaults to 20 and accepts 2 to 500. A short period reacts quickly but sits on a small sample whose standard deviation is easily small, which exaggerates spikes; a long period gives a stable baseline, produces lower readings for the same raw volume and delays the first value by the length of the window.
| Parameter | Type | Default | Range |
|---|---|---|---|
| Period | number | 20 | 2 – 500 |
What it does not show
Volume distributions are typically skewed to the right rather than symmetric, so a z-score here is a standardized distance and not a probability or a percentile. A single outlier inside the window raises the dispersion enough to hide the next genuine spike. The window is a fixed count of preceding bars with no session reset, so bars just after an open are compared against an overnight stretch that traded on very different terms. The series also carries no direction: an extreme reading says nothing about who was buying or selling, and blank values on thin instruments mean the reference had no dispersion to divide by.
Using it in Senzoukria
Add it from the Indicators panel of any footprint chart or candle chart. It runs on futures data from Rithmic or Databento and on crypto pairs from Binance and Bybit, on the same engine — the calculation does not change with the venue, only the data feeding it does. Market data subscriptions are billed by the provider, separately from the app.
Related indicators
- Tape Speed — Tape & flow
- Diagonal Imbalances — Tape & flow
- Stacked Imbalances — Tape & flow
- Absorption Score — Tape & flow
- Unfinished Auctions — Tape & flow
- Effort vs Result — Tape & flow
See the full indicator library, or start with the order flow guide if you are new to reading aggression, delta and absorption.
Frequently asked questions
- What is a good volume z-score threshold?
- There is no universal level. What counts as extreme depends on the period you chose, on the instrument and on the time of day, because the reference is only the preceding bars. A practical approach is to observe which readings correspond to bars you already consider unusual on your own chart, then use that range as your own reference.
- Why is the volume z-score blank on some bars?
- Two situations produce no value. The first is warm-up: the bar does not yet have a full window of preceding bars, so no mean or dispersion can be computed. The second is a window where volume is identical on every bar, which makes the standard deviation zero and the ratio undefined, so nothing is plotted rather than a misleading zero.
- Is volume z-score the same as relative volume?
- No. Relative volume is usually a ratio of current volume to an average, often compared against the same time of day on previous sessions. A z-score divides the deviation from the mean by the dispersion of the last N bars, so it accounts for how variable volume has recently been, and its window is a plain count of preceding bars rather than a time-of-day profile.