TPO Chart Construction and Value Area Mechanics

A TPO (Time Price Opportunity) chart assigns a letter to each 30-minute bracket of a session — A for the first 30 minutes, B for the next, and so on. Each letter prints at every price traded during that bracket. The resulting horizontal distribution is the Market Profile: a bell curve showing where price spent time, not where volume traded.

How TPOs print

Each 30-minute period produces a vertical column of letters at every price touched. The first time price visits a new level, it prints a single print. As the session rotates back through familiar prices, those levels accumulate stacked letters. Single prints at the extremes mark range extension driven by aggression; fat clusters in the middle mark acceptance.

Building the Value Area

The Value Area (VA) is the price range containing 70% of the session's TPOs — roughly one standard deviation. Construction is iterative:

1. Identify the price with the most TPOs (the TPO POC).
2. Count TPOs in the two prices immediately above and below; add the larger.
3. Continue expanding outward, always adding the larger of the next-up or next-down total, until you reach 70% of total TPOs.
4. The highest and lowest prices included become VAH and VAL.

This rotation method differs from a simple volume histogram. A price can host many TPOs (time) with little actual volume, flagging low-participation acceptance.

Reading rules that matter

• Wide VA (>1.5× the 20-day average): balanced, indecisive day. Fade extremes toward POC.
• Narrow VA (<0.7× average): directional day. Trade with the drive, do not fade.
• Single prints above VAH: buyer extension. If the next session fills them, value is migrating up.
• POC migration across 3+ sessions: trend confirmation. Align entries with the migration direction.

A practical read

Start every session by marking the prior day's VAH, VAL, and POC. Track today's developing POC — if it prints above yesterday's POC by the end of B-period (one hour), the auction is repricing higher. Build longs on pullbacks to the developing POC, stop 1×ATR beyond the prior VA. TPO construction turns raw time-at-price into a map of acceptance the volume histogram alone cannot draw.