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Session Mid — Structure & sessions, on the price chart.
What Session Mid measures
The value is (running high + running low) / 2, measured from the 17:00 CT session open and recomputed as new extremes appear. It is a geometric centre, not an average of traded prices and not volume-weighted: the line moves only when one of the two extremes moves, so an hour spent trading inside the existing range leaves it exactly where it was. Like the extremes it is built from, it is defined on the first bar of a session and needs no warm-up.
The formula, as implemented
This is not how the indicator is usually defined elsewhere — it is what the shipped code computes, documented next to the implementation:
Milieu de session « developing » : (running high + running low) / 2 — la médiane du range de session en construction, reset à chaque ouverture (17:00 CT). Défini dès la 1ʳᵉ barre — pas de warm-up (extrême courant, pas une moyenne).
How to read it
- The close sitting above the line means the session is currently trading in the upper half of its own range; below the line, the lower half.
- The line steps rather than drifts. Each step is a new session extreme, and between steps it is a fixed price.
- Price oscillating around a flat midpoint for an extended stretch is a session in balance around that price.
- When the midpoint and the session VWAP separate, volume is concentrated on one side of the range: the midpoint ignores how much traded, VWAP does not.
- A midpoint that steps repeatedly in one direction means the extreme on that side keeps being extended — the range is expanding, not rotating.
Parameters and defaults
Smoothing is set to 1 out of the box and the line is drawn raw. Values up to 200 average it over that many bars, which rounds the steps into a curve and delays its reaction to a new extreme by roughly half the averaging window. The neutral grey (#9e9e9e) is chosen so the line stays readable behind price without competing with the session high and low lines.
| Parameter | Type | Default | Range |
|---|---|---|---|
| Smoothing | number | 1 | 1 – 200 |
What it does not show
The midpoint is derived from exactly two prices, so it is blind to volume, to how long price spent at each level, and to the aggressor side. A single tick beyond the previous extreme moves it for the remainder of the session, even if nothing traded there afterwards. When the chart's history begins mid-session, the extremes come only from the loaded bars and the midpoint for that session is not the one a complete session would produce. It is not a value area: for a fair-value reference weighted by time or volume, use the profile tools instead.
Related indicators
- Prior Week High/Low — Structure & sessions
- Engulfing — Structure & sessions
- Pin Bar — Structure & sessions
- Inside Bar — Structure & sessions
- Outside Bar — Structure & sessions
- Doji — Structure & sessions
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Frequently asked questions
- What is the session midpoint?
- It is the halfway price between the highest and lowest prices traded so far in the session. On this chart it is computed from running extremes anchored to the 17:00 CT open, so it reflects only what has already happened, not the session's final range.
- Is the session midpoint the same as VWAP?
- No. The midpoint averages two prices — the session high and low — and ignores volume entirely. VWAP averages every traded price weighted by the volume behind it. They coincide only by accident, and the distance between them shows where the session's volume is concentrated within its range.
- Why does the session mid line jump instead of moving smoothly?
- It changes only when a new session high or low prints, and each new extreme shifts the midpoint by half the amount the range extended. Between extremes the line is constant, which produces steps rather than a curve.