The Cost Performance Index is a key metric used to measure progress on a project. It’s measured by calculating the ratio between the cost of work done and the planned cost for that work. In other words, it looks at how much work has been completed in relation to the budget. This formula helps to show the overall performance of a project over time, giving visibility into cost control measures and providing feedback on project performance. The higher the number, the better – it means you’re getting more bang for your buck! The Cost Performance Index is an essential tool for effective project management.