80% value area rule
The 80% value area rule is a market profile heuristic stating that when price opens outside the previous session's value area, then trades back inside it and is accepted there, the session is expected to rotate across the whole value area to the opposite edge. The 80% figure is the rule's traditional name, not a measured statistic.
Senzoukria · Glossary · Updated September 2026
The rule as usually stated
Take the previous session's value area, the band that held about 70% of that session's volume between VAH and VAL. If the current session opens above or below that band, the rule watches for price to come back inside it. Acceptance inside value, traditionally measured as two consecutive 30-minute TPO brackets trading within the band, is the trigger. The expectation is then a rotation through the value area to its other edge.
The name comes from the claim, repeated in Market Profile literature, that the rotation completes in most cases. That figure is part of the folklore of the method; it is not a statistic Senzoukria has measured, and no success rate is asserted here.
- Reference: the previous session's VAH and VAL.
- Condition: open outside value, then re-entry with acceptance.
- Expectation: rotation toward the opposite edge of value.
Why it makes auction sense
An open outside value is an attempt to establish new value elsewhere. If that attempt fails and price is accepted back inside yesterday's band, the auction is saying that the previous value still holds, and inside a balanced value area price tends to rotate between the edges. The rule is therefore a restatement of the balance read described in the senzoukria.com guide on volume profile: inside value, VAL is support, VAH is resistance and the POC is the mean.
What the rule does not say matters as much: an open outside value that is accepted outside is the imbalance case, and the rule does not apply.
In Senzoukria
The Session VAH/VAL (developing) indicator draws the value area edges of the cumulated session profile using the Steidlmayer algorithm (start at the POC, extend two ticks on the side with more volume until 70% is reached, ties resolved upward). The previous session's final edges are the references the rule uses; the current session's developing edges show where value is forming now. Session POC (developing) adds the point of control.
The Market Profile (TPO) indicator with a 30-minute bracket, which the app calls the Steidlmayer standard, reproduces the bracket-based acceptance test. Whether re-entry is being accepted is read from the footprint at the edge, with the delta convention that delta equals ask volume minus bid volume per level.
Common mistakes
- Quoting 80% as a measured probability. It is the rule's traditional name; treat it as a hypothesis to test on your own data.
- Applying the rule when price merely pokes into value. The rule requires acceptance, not a touch.
- Using the wrong value area: the reference is the previous session's, built on the same session definition (the app anchors CME sessions at 17:00 CT).
- Ignoring the day type. On a strongly imbalanced day the re-entry never happens, and the rule is silent, not wrong.
Related
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Frequently asked questions
- What are the conditions of the 80% value area rule?
- Price must open outside the previous session's value area, come back inside it, and be accepted there, traditionally two consecutive 30-minute brackets trading inside the band. Once those conditions are met, the rule expects a rotation to the opposite edge of the value area. It does not apply if price is accepted outside value.
- Is the 80% figure reliable?
- It is the rule's conventional name from Market Profile literature, not a statistic measured on current markets or by Senzoukria. The auction logic behind the rule is sound: value that is re-accepted tends to be rotated through. How often that completes on a given instrument and period is something to measure on your own data rather than assume.