The trade volume index (TVI) measures the amount of money flowing in and out of a security or the market. The TVI depends on the direction of the security and whether securities are accumulated or distributed. The TVI generally uses a security's intraday price data.

To calculate the TVI, the minimum tick value of the security must be known. Next, the change in price must be calculated by subtracting the last price from the most current price. Then, the direction must be determined. If the change in the security's price is greater than the minimum tick value, the security is in an accumulation period. If the change in the security's price is less than the minimum tick value, the security is in a distribution period. If the change is less than or equal to, or greater than or equal to, the minimum tick value, the security's direction is the same as the last direction.

When the direction is determined, the TVI can be calculated. If the security is in accumulation, the current TVI is the previous trade volume index plus the current day's volume. Conversely, if the security is in distribution, the TVI is the previous trade volume index less the current day's volume.

The TVI can be used to indicate buying or selling pressure within a security. Say, for example, the changes in the prices of the security are greater than the minimum tick value and have been rising over a six-hour period. This signals traders and investors are accumulating the security and buying at the ask. This can be interpreted as bullish activity and may signal the security could increase in price due to the buying pressure.