73. Calculating Speed Index
1. Take the duration until the page is visually
complete, above the fold
2. Separate it into 100ms intervals
3. For each interval, assign it a “percent
visually complete”
4. Invert that percentage so it’s “percent
incomplete” or “percent remaining”
5. Multiply that by the interval length (100ms)
6. Sum all of the intervals. Speed Index!
Mobile viewport size
will affect this metric!