Calculate both averages from the same observations
Assume three complete consecutive one-minute intervals in one session, with the chosen representative prices and volumes below. These are hypothetical observations. Use exactly the same prices for both calculations so the only difference is weighting. A representative bar price is a sampling choice, not a reconstruction of every trade inside the bar.
- Equal-interval TWAP = sum(P) / number of intervals = 306 / 3 = $102. Each minute receives one-third of the weight.
- Bar-based VWAP = sum(P × V) / sum(V) = 103,400 / 1,000 = $103.40. The final minute receives 800 / 1,000 = 80% of the weight.
- The $1.40 difference reflects heavier volume at the highest sampled price. It does not identify who traded or predict the next price.
- If each interval instead had 100 shares, VWAP would also be $102. If all three prices were $100, both averages would be $100 regardless of positive volume differences.
| Interval | Price P | Volume V | P × V |
|---|---|---|---|
| 09:30 to 09:31 | $100 | 100 shares | 10,000 |
| 09:31 to 09:32 | $102 | 100 shares | 10,200 |
| 09:32 to 09:33 | $104 | 800 shares | 83,200 |
| Total | $306 summed samples | 1,000 shares | 103,400 |