The calculation (and why the anchor is everything)
VWAP — volume-weighted average price — is the running average of traded price weighted by volume: Σ(price × volume) / Σ(volume). Institutions benchmark executions against it, which is what gives the line its gravitational pull intraday.
The formula never changes. What changes is the anchor — the moment the sums reset to zero. Move the anchor and the same formula draws a completely different line, watched by a different audience.
Globex (full-session) VWAP
Anchors at the futures session open: 5:00 PM CT / 6:00 PM ET. It averages the entire overnight and day session — the complete auction. Overnight and 24-hour traders live on this line, and after a quiet night it converges toward the day-session VWAP anyway. Its weakness: on a big overnight move, the accumulated overnight volume drags the average away from where day-session participants perceive value.
RTH (day-session) VWAP
Anchors at the regular trading hours open — 9:30 AM ET for equity index futures (ES, NQ, YM, RTY). Note that RTH differs by product: crude oil's pit session opens 9:00 AM ET, treasuries and metals have their own conventions. RTH VWAP reflects only day-session business, which is why many day traders prefer it: it's the average the cash-session institutions are being benchmarked against. On the open it starts fresh and whips; it earns trust as the session builds volume.
Weekly and Monthly VWAP
Anchor at the first Globex open of the week (Sunday evening) or of the month. These are swing references: a market holding above a rising weekly VWAP is being accumulated on the week; the monthly line often marks where longer-horizon positioning defends. They move slowly, which is the point — they filter intraday noise into a position-trader's frame.
Anchored VWAP
Anchors wherever you choose: an FOMC statement, a breakout bar, a swing high or low, an earnings-adjacent gap. The logic: everyone who traded since that event has an average price, and anchored VWAP is that average. Price returning to an event-anchored VWAP is revisiting the crowd's break-even from that event — a natural decision point. It's the most flexible anchor and the most abused; anchor to events that mattered, not to every swing.
Sigma bands
Most serious VWAP implementations draw volume-weighted standard deviation bands (±1σ, ±2σ, ±3σ) around the line. Because they're computed from the session's actual dispersion, they adapt: tight bands signal acceptance (rotational day), expanding bands signal directional conviction. Common reads: first touch of +2σ in a rotation fades back toward VWAP; riding the +1σ rail with shallow pullbacks is trend behavior — don't fade it.
Implementation details that bite
- Tick data vs minute bars. A VWAP summed from every tick is the true line; one built from 1-minute bars (typical price × bar volume) is an approximation that drifts on fast days. For session VWAPs the difference is visible; for weekly/monthly it mostly washes out.
- Session templates. A "daily" VWAP anchored at midnight — the default on some platforms — matches neither the Globex nor the RTH audience. Know your anchor.
- Timeframe independence. A correct VWAP shouldn't change when you switch your chart from 1-minute to 5-minute bars. If it does, it's being computed from the chart's bars rather than from the underlying tape.