Quantify the initial-load saving from lazy loading below-the-fold assets.
Lazy loading removes off-screen images from the initial load entirely. Because most users never scroll to the bottom, a large share of deferred weight is never downloaded at all. Lazy loading above-the-fold images harms LCP, which is why the loading attribute should be set to eager for the hero image.
Lazy Load Savings
Initial saving = deferred images × average size; never-loaded weight depends on scroll depth
Initial saving = deferred images × average size; never-loaded weight depends on scroll depth Lazy loading removes off-screen images from the initial load entirely. Because most users never scroll to the bottom, a large share of deferred weight is never downloaded at all.
Lazy loading above-the-fold images harms LCP, which is why the loading attribute should be set to eager for the hero image.
This calculator takes 5 inputs: Total images on the page, Images above the fold, Average image size, Connection speed, Average scroll depth. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.