Work out lazy load benefit instantly with clear inputs, formula shown and shareable results.
Lazy loading defers everything below the fold, so the initial payload is only the visible images and the deferred weight is the rest. On a long gallery page lazy loading can cut the initial payload by 85%, and images above the fold should be excluded so they are not delayed.
Initial payload
initial KB = images above the fold x average image weight
Deferred
deferred = (total images - above the fold) x average weight
initial KB = images above the fold x average image weight. Lazy loading defers everything below the fold, so the initial payload is only the visible images and the deferred weight is the rest.
On a long gallery page lazy loading can cut the initial payload by 85%, and images above the fold should be excluded so they are not delayed.
Enter images on the page, images visible without scrolling, average image weight. The defaults shown are a realistic worked example — swap in your own figures to get a result you can use.