The Value Area (VA) is the contiguous price range within a Market Profile or Volume Profile that contains a defined share — conventionally ~70% — of the session's trading activity (TPO counts in classic Market Profile, or traded volume in a Volume Profile). It is centered on the Point of Control (POC), the single price with the most activity, and bounded by the Value Area High (VAH) and Value Area Low (VAL). Conceptually it answers "where did the market agree value was?" — the zone of acceptance, as opposed to the thin tails above VAH and below VAL where price was rejected. Its core tension: the 70% figure and the levels it produces feel statistically precise, but the threshold is a definitional convention (a normal-distribution analogy), not a measured optimum, and the price levels are an artifact of how the profile is bucketed.

How it's calculated / formed

The Value Area is built by expanding outward from the POC until the chosen percentage of total activity is captured. The classic CBOT / Steidlmayer (TPO) algorithm, as taught by Jim Dalton in Mind Over Markets, works in pairs of rows:

1. Total the activity (TPO count or volume) across all price levels and multiply by the target share (default 0.70) to get the threshold. 2. Start the running total at the POC's activity. 3. Compare the two price rows immediately above the current VA against the two rows immediately below. Add whichever pair has the greater combined activity to the VA and to the running total. 4. Repeat step 3, always taking the larger adjacent pair, until the running total ≥ threshold. 5. The highest price now included is VAH; the lowest is VAL.

Many modern Volume Profile implementations simplify this to expanding one row at a time (take the single higher-volume neighbor each step) rather than in pairs — results are usually close but not identical, and the choice of row/tick bucket size shifts the levels. The percentage is configurable on virtually every platform; 70% is the default, but some traders use 68% (the textbook one-σ figure) or other values.

The 70% basis: Steidlmayer modeled the daily auction as an approximately Gaussian (bell-shaped) distribution and identified the Value Area with the first standard deviation. One σ of a normal distribution is ~68.2%, which is rounded in practice to 70%. So "70%" and "one standard deviation" are used interchangeably in the literature, with the small discrepancy being the rounding. This is an analogy, not a fitted statistic — intraday distributions are frequently skewed, bimodal, or fat-tailed, so the "standard deviation" framing is descriptive rather than literal.

How it's used in practice

• VAH and VAL as support/resistance. The value-area edges are watched as reaction levels: price approaching VAL from inside often finds support; approaching VAH often finds resistance. They are among the most-watched intraday levels in futures.
• "Inside / above / below value" as a context regime. Traders classify the current price relative to the prior session's value area to set a directional bias: trading above prior VAH suggests buyers have accepted higher prices (bullish acceptance / value migrating up); below prior VAL suggests the reverse; inside value implies balance / rotation, favoring fade-the-edges (mean-reversion) tactics over trend tactics. Where the day opens relative to prior value (open-drive vs open inside value) feeds the same read.
• The 80% Rule. A widely cited Market Profile heuristic: if price opens outside the prior day's value area, then trades back inside and stays inside for two consecutive TPO periods (two 30-minute bars), there is a high (~80%) probability it will traverse the full value area — i.e. travel from one edge to the other (VAH↔VAL). The two-period requirement is meant to confirm acceptance rather than a brief poke. It is used as a setup for a move toward the opposite value-area edge.
• Value-area migration. Comparing today's VA to yesterday's (higher, lower, overlapping, or "inside") is read as the auction's developing direction.

The exact swing entries, stops, and hold logic that build on these reads are deferred to the Swing Trading branch — this node defines the levels and their context meaning, not the trade mechanics.

Standing & evidence

Value Area is standard, institutionally adopted vocabulary in futures and increasingly in equity intraday analysis — it is a core construct of Auction Market Theory, not a fringe indicator. That much is uncontested.

The specific numbers deserve honest caveats:

• The 70% threshold is a convention, justified by the normal-distribution analogy, not by an out-of-sample optimization showing 70% is the "best" level. Treat it as a sensible default, not a proven edge boundary.
• The 80% Rule is a practitioner heuristic with little rigorous, published base-rate validation. The "~80%" figure is folklore-grade — widely repeated, rarely measured. What testing exists is unflattering: analyses of E-mini S&P 500 futures have reported the setup completing the full value-area traversal closer to ~60% of the time, prompting the quip that it "should be called the 60% rule." Exact figures vary by instrument, definition of "acceptance," and sample, and no canonical study establishes a stable rate. So: real, tradeable tendency — but the headline 80% is unsupported, and the rule is conditional on regime (works better in rotational/balanced sessions, fails in strong trend days that simply leave value behind).

Strengths & limitations

Strengths: Gives objective, repeatable levels (VAH/VAL/POC) that many participants watch, so they carry some self-fulfilling weight; cleanly separates "acceptance" zones from "rejection" tails; the inside/above/below-value framing is a genuinely useful context filter for choosing between mean-reversion and trend tactics.

Limitations / failure modes:

• Garbage-in on the period and bucket. A value area is only meaningful relative to a chosen session/window and tick-bucket size — change them and VAH/VAL move. A VA computed over the wrong window is misleading.
• Trend days break it. On strong directional days the auction does not rotate; price runs through prior value and never returns. Fading VAH/VAL or expecting an 80%-rule traversal then bleeds.
• The most common misuse: treating the 70% and 80% figures as measured probabilities rather than the convention and heuristic they are, and sizing as if the level "should hold." It's context, not a guarantee.

Sources

• Wikipedia — Market profile (origin: J. Peter Steidlmayer / CBOT, public release 1985; value area ≈ first standard deviation, ~68%, "Gaussian distribution" framing).
• marketprofile.info — Value Area Explained: VAH, VAL, and POC (expand-from-POC algorithm; 70% as one-σ convention).
• Overcharts Help Center — Volume Profile: Value Area (VA ≈ 70% of volume around POC; VAH/VAL definitions).
• TradingView — Volume profile indicators: basic concepts (VA as % of volume in range, threshold configurable, default 70%).
• mypivots.com — 80% Rule definition (two consecutive 30-min bars back inside value; "high probability" of filling the VA) and the empirical pushback that E-mini testing puts completion nearer 60%.
• Jim Dalton, Mind Over Markets / Markets in Profile (canonical pair-expansion VA construction and acceptance/inside-value framework — referenced via the above secondary sources).