In trading, price tells you what the market is paying, but volume tells you how much conviction is behind that price. The Volume Weighted Average Price, or VWAP, combines these two critical pieces of data into a single, powerful benchmark.

Think of it like calculating the average price of gasoline you bought over a month. A simple average would just add up the prices of each purchase and divide by the number of times you filled up. But that doesn't tell the whole story. What if you bought 5 gallons when the price was high but 15 gallons when it was low?

VWAP accounts for this difference. It gives more weight to the prices at which more trading occurred. A price backed by high volume has a greater impact on the VWAP than a price where only a few shares traded hands. This makes it a truer representation of an asset's average price for a given period, typically a single trading day.

The VWAP calculation is a cumulative process that resets at the start of each trading day. For every transaction, you multiply the price of the trade by the number of shares traded. You keep a running total of this value throughout the day, as well as a running total of the volume.

At any point, you can calculate the current VWAP by dividing the total dollar value traded by the total volume traded up to that point. The process is straightforward and can be broken down into three steps for any given time interval (like one minute or five minutes).

Let's walk through a simplified example over three, one-minute intervals:

1. Minute 1: Price is $100, Volume is 500 shares. The cumulative price-volume is $100 \times 500 = 50,000$. The cumulative volume is 500.
2. Minute 2: Price is $101, Volume is 1,000 shares. The new price-volume is $101 \times 1,000 = 101,000$. Cumulative price-volume becomes $50,000 + 101,000 = 151,000$. Cumulative volume is $500 + 1,000 = 1,500$. The VWAP is now 151,000 / 1,500 = \100.67.
3. Minute 3: Price is $100.50, Volume is 200 shares. The new price-volume is $100.50 \times 200 = 20,100$. Cumulative price-volume becomes $151,000 + 20,100 = 171,100$. Cumulative volume is $1,500 + 200 = 1,700$. The final VWAP is 171,100 / 1,700 = \100.65.

Notice how the high volume at $101 pulled the average up significantly in the second minute.

VWAP serves as a dynamic, intraday benchmark for the "fair" price of a security. Large institutional buyers, like pension funds and mutual funds, often use it to evaluate the quality of their trade executions. If they buy below the VWAP, they got a good deal relative to the average participant that day. If they buy above it, they overpaid.

This is because the VWAP line represents a sort of financial center of gravity for the day's trading activity. When the price moves far away from it, it often has a tendency to return. This concept of price reverting to the VWAP is a fundamental principle many traders watch for.

Because it incorporates volume, VWAP provides a more complete picture than a simple moving average. It tells you not just the average price, but the average price where most of the day's business has been conducted.

By understanding what VWAP is and how it's calculated, you have a solid foundation for interpreting intraday price action.