Break LCP into its component phases and find which one to optimise.
Breaking LCP into its four phases identifies where the time actually goes. A large load delay usually means the resource is discovered late and can be fixed with a preload hint alone. LCP is the heaviest-weighted Core Web Vital, and the 2,500 ms threshold applies at the 75th percentile rather than the average.
Largest Contentful Paint
LCP = TTFB + resource load delay + resource load time + element render delay
LCP = TTFB + resource load delay + resource load time + element render delay Breaking LCP into its four phases identifies where the time actually goes. A large load delay usually means the resource is discovered late and can be fixed with a preload hint alone.
LCP is the heaviest-weighted Core Web Vital, and the 2,500 ms threshold applies at the 75th percentile rather than the average.
This calculator takes 4 inputs: Time to first byte, Resource load delay, Resource load time, Element render delay. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.