We pulled load time and conversion data across 40 client websites spanning ecommerce, lead gen and SaaS to see how strong the relationship actually is.
Below 1.5 seconds, further speed gains showed diminishing conversion returns. Between 1.5 and 2.5 seconds, we still saw a measurable, near-linear relationship.
Above 2.5 seconds, the drop-off accelerated sharply — every additional second cost noticeably more conversion rate than the one before it.
The practical takeaway: 2.5 seconds isn't just a Core Web Vitals threshold, it's roughly where the business cost of slowness starts compounding.