# Midpoint/half-back of Session

A Volume & Order Flow concept (VWAP family) in the LuxAlgo Library, with 1 indicator implementation.

## What is the Midpoint/half-back of a Session?

The session midpoint, called half-back in futures floor slang, is the halfway point of a session's range: the session high plus the session low, divided by two. It is a live level that shifts with every new session high or low, and it splits the session's auction into halves. Price holding above half-back is read as buyers keeping control of the range; price trading below it is read as handing the lower half to sellers.

The label comes from the trading floor. Half-back is old futures slang for price pulling halfway back into the session's range, and the level is a fixture of Market Profile practice, the auction framework J. Peter Steidlmayer developed at the Chicago Board of Trade in the 1980s, where the developing range's midpoint is checked against where the bulk of business is being done. Floor traders tracked the day's high, low, and half-back because those were references a trader could hold in mind without a screen, and the level survives because it still answers the same question, which side controls the session's range, using nothing more than an average of two prices.

Because it needs nothing but the high and low, the midpoint is drawn per session (Asia, London, New York) and often carried into later trading sessions as a reference; the Asia midline indicators in this category do exactly that. The same 50% logic appears elsewhere: it is the equilibrium of a range in premium-and-discount frameworks, and it is the price-only cousin of [session VWAP](https://www.luxalgo.com/library/concept/session-vwap/), which weights by volume instead of treating the range as symmetric.

That symmetry assumption is the level's main limitation and the reason it pairs naturally with volume tools. The midpoint says nothing about where trade actually concentrated: a session can spend hours grinding near its low, and the geometric mid will still sit halfway up the range. A [volume profile](https://www.luxalgo.com/library/concept/volume-profile/) of the same session shows the [point of control](https://www.luxalgo.com/library/concept/point-of-control/) and [value area](https://www.luxalgo.com/library/concept/value-area/) where volume really accumulated, and a [TPO profile](https://www.luxalgo.com/library/concept/tpo-profile/) shows the equivalent by time. When the geometric mid and the volume-based references agree, the middle of the range is well defined; when they sit far apart, the session is lopsided and the midpoint is the weaker of the two reads.

## How to identify the session midpoint on a chart

The level is fully mechanical, so identifying it is a matter of defining the session correctly and updating the line as the range grows.

1. Define the session window in exchange or local time (for example Asia 00:00-08:00, London 08:00-16:00) and track its running high and low.
2. Plot (session high + session low) / 2 as a horizontal line across the session; recompute every time a new session high or low prints, so the line steps as the range expands.
3. At session close, freeze the level and carry it forward alongside the session high and low; the completed Asia mid carried into London and New York is the classic use.
4. Read interaction rather than touches: bars closing and holding on one side keep that side in control, while fast wicks through the line followed by a reclaim read as rejection.
5. Cross-check the mid against volume references such as an [anchored VWAP](https://www.luxalgo.com/library/concept/anchored-vwap/) from the session open; agreement tightens the zone, and wide disagreement flags a lopsided session.

## How it's calculated

The session midpoint, or half-back, is the level halfway between the session's high and its low.

```
1. Fix the session window, from the session open to the session close (e.g. the instrument's regular trading hours).
2. As each bar t of the session completes, update the running extremes: H_sess = max(H_sess, H_t) and L_sess = min(L_sess, L_t).
3. Compute Mid_t = (H_sess + L_sess) / 2.
4. Plot Mid_t as a horizontal level; it moves only when a new session high or low prints and becomes final at the session close.
5. Optionally keep the prior session's final midpoint on the chart as a static reference during the current session.

  t: bar index within the session
  H_t: high of bar t
  L_t: low of bar t
  H_sess: running highest high of the session so far
  L_sess: running lowest low of the session so far
  Mid_t: session midpoint (half-back) at bar t
```

Known as half-back (HB) in Market Profile terminology.

It is a pure range midpoint: volume plays no part, so it usually differs from VWAP and from the POC.

Any fixed session definition works (RTH only, full 24h day, week), as long as the extremes are tracked over that window.

## How traders use it

- As an intraday bias line: acceptance above the session midpoint favors rotations toward the session high, while losing it opens rotation into the lower half; it is a reference, not a wall, and trend days can slice through it without pause.
- As a pullback location: on directional days, retracements to half-back are a classic spot to look for responsive buyers or sellers, usually with confirmation rather than blind fills.
- As a carried-forward level: the midpoint of a completed session (the Asia mid is a common example) is watched in following sessions for reactions, alongside that session's high and low.
- As a confluence layer: a session mid landing on a [high-volume node](https://www.luxalgo.com/library/concept/high-low-volume-nodes/) or inside the value area marks a middle that both price geometry and participation agree on, which makes reactions there more informative than either reference alone.
- As a target inside balance: in rotational sessions, responsive trades taken at the session extremes commonly use half-back as the first objective, with the opposite extreme as the second if the mid gives way.

## Session midpoint vs related session references

- **Session VWAP** (https://www.luxalgo.com/library/concept/session-vwap/): The midpoint averages two prices, the extreme high and the extreme low; session VWAP averages every trade, weighted by size. VWAP tracks where business was actually done while the mid treats the range as symmetric, so on lopsided sessions the two separate, and the gap between them describes the imbalance.
- **Point of Control** (https://www.luxalgo.com/library/concept/point-of-control/): The point of control is the single price with the most traded volume in the session, a magnet defined by participation. The midpoint is defined by geometry alone. A mid sitting on the POC marks a well-agreed middle; a mid far from it says the range's center and the auction's center disagree.
- **Value Area** (https://www.luxalgo.com/library/concept/value-area/): The value area spans the prices holding roughly 70% of the session's volume, a band rather than a line. Half-back can fall inside or outside it: inside, it is another middle-of-value reference; outside, price crossing the mid is traveling through low-participation territory and tends to move faster.

## FAQ

### Is the session midpoint the same as VWAP?

No. The midpoint is purely geometric, the average of the session high and low, so a single extreme print moves it. VWAP averages every trade weighted by volume, so it tracks where business was actually done. On balanced days the two often sit close together; on trend days they can diverge widely, and that gap is itself information.

### Why is the session midpoint called half-back?

Half-back is trading-floor shorthand for the 50% retracement of the day's or session's range: price pulling halfway back into the move. The term survives in futures and Market Profile circles, where traders describe a rally or break as holding or losing half-back as a quick gauge of which side still controls the session.

### How do you calculate the session midpoint?

Add the session's high to its low and divide by two. The level is live while the session runs, stepping up with each new high and down with each new low, and it freezes at the session close. There are no parameters beyond the session definition itself, which is why the calculation is identical across platforms.

### Which session midpoints do traders watch most?

The Asia session mid is the most commonly carried level, because Asia often builds a balanced overnight range that London and New York then break or respect. The prior day's mid and the London mid are also widely used. Which matters most depends on the instrument: index futures traders lean on the overnight mid, while forex traders more often reference the Asia range.

### Is half-back the same as a 50% Fibonacci retracement?

Arithmetically both mark a halfway point, but of different things. Half-back divides the session's high-low range; a 50% retracement divides a chosen swing, which may start or end outside the session. When the measured swing happens to be the session range itself, the two levels coincide exactly.

### Is the session midpoint better than VWAP?

Neither dominates; they answer different questions. The mid locates the center of the range, VWAP the volume-weighted average price of the session's trade. Many session traders keep both and pay particular attention when they converge, or when price gets caught between them. There is no evidence that one systematically outperforms the other as a standalone level.

## Implementations in the Library

- Midpoint/half-back of Session (LuxAlgo): https://www.luxalgo.com/library/indicator/midpoint-half-back-of-session/

## Related concepts

- VWAP Bands: https://www.luxalgo.com/library/concept/vwap-bands/
- Anchored VWAP: https://www.luxalgo.com/library/concept/anchored-vwap/
- Session VWAP: https://www.luxalgo.com/library/concept/session-vwap/
- Periodic VWAPs: https://www.luxalgo.com/library/concept/periodic-vwaps/
- Rolling VWAP: https://www.luxalgo.com/library/concept/rolling-vwap/
- VWAP Mean-reversion vs Trend Regimes: https://www.luxalgo.com/library/concept/vwap-mean-reversion-vs-trend-regimes/
- VWAP Pinch: https://www.luxalgo.com/library/concept/vwap-pinch/

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Source: https://www.luxalgo.com/library/concept/midpoint-half-back-of-session/ (LuxAlgo Library, the encyclopedia of trading & technical analysis). Free to use with attribution: https://www.luxalgo.com/library/license/