Schedule Performance Index (SPI)

The Schedule Performance Index (SPI) is a key figure from the earned value analysis. It measures how well a project is keeping to its schedule by relating the value of the work performed to the work that should have been completed by the status date.

An SPI of exactly 1 means the project is exactly on plan. A value above 1 indicates that it is ahead, a value below 1 that it is behind. Together with the Cost Performance Index, the schedule and cost situation of a project can be assessed reliably.