Calculate SPI

I found an article about the different measures for the projects. One is the SPI, which is a way to know the advance of the project but not the total task and durations, the idea is to compare the actual situation versus the plan.

So imagine if there are 10 tasks. The team just finish 4. But according to the project dates, the team should complete 5 tasks today. So the progress of the project is 40% but the SPI is (4/5) = 80%.

How can I calculate this measure

https://www.wrike.com/project-management-guide/faq/how-to-calculate-earned-value-in-project-management/

Schedule Performance Index (SPI): This measure is similar to SV but is often preferred as it translates the numbers into a value that is easily compared across tasks or projects. The SPI calculation is: SPI = EV/PV. When SPI is above 1.00, you’re ahead of schedule. If it’s below 1.00, you’re behind. To take the example from above, SPI would be 1/2 = 0.5. Using SPI is different than simply comparing your progress against your baseline. Comparing your actual schedule against your plan may indicate you’re behind on two tasks. So, you know where your immediate problem is, but not necessarily how it impacts the overall project or your expected completion date. Using earned value, you can calculate your SPI both by task and for the project as a whole. When you take the SPI for each task and look at the bigger picture, you can see that your project is ahead of schedule, even with two late tasks. This helps you better understand the overall impact of the late tasks on the project.