VWAP execution: how large orders track the day's average price

Many traders know this measure as a chart line. For large investors, it is also a way to execute big orders and a yardstick to judge them. This page explains VWAP execution, how it works and where it falls short.

Quick answer

VWAP execution is a trading strategy that splits a large order into smaller pieces and times them to match the market's expected trading volume through the day. The goal is to buy or sell at an average price close to the day's volume-weighted average price (VWAP). Because it trades more when the market is busy and less when it is quiet, it aims to reduce price impact.

Key takeaways

• It weights each price by the volume traded at it.
• VWAP execution follows the market's volume pattern.
• It aims to get an average price near the day's VWAP.
• Institutions also use it as a benchmark for traders.
• It does not protect against strong price trends.

What is VWAP?

The volume-weighted average price is the average price of a share over a period, where each trade counts in proportion to its size. You multiply each trade price by its volume, add them up and divide by total volume.

Prices at which many shares traded count more than prices with little trading. This makes it a fair picture of the 'typical' price paid by all market participants during the day.

How does VWAP execution work?

Trading volume in Indian shares usually follows a pattern: busy at the open, quieter around midday and busy again near the close. The algorithm uses past data to estimate this pattern for the share.

It then splits the order to match. If 15 percent of a day's volume usually trades in the first half hour, the algorithm aims to complete about 15 percent of the order in that time. This keeps the order a steady share of market activity.

Why do institutions use it?

It reduces price impact, because the order is spread in line with available liquidity. It also gives a clear benchmark. If a trader buys below the day's VWAP, the execution is seen as good. If above, it may need review.

This benchmark is simple to measure and understand, which is why many fund houses and brokers use it to judge their trading desks.

What are the limits?

This method follows the market rather than making a judgement. If a share rises strongly all day, a buy order matched to the day's average will still pay rising prices. A trader with a strong view might do better trading faster or slower.

The benchmark can also be gamed in theory, since a large order is itself part of the day's volume. And because the measure starts from the order's start time, it ignores costs from any delay before the order was placed, which implementation shortfall captures.

VWAP for chart traders

On charts, intraday traders use the VWAP line as a reference for whether price is above or below the day's average. That use is different from execution, though both rely on the same calculation.

Frequently Asked Questions