What a fast website is actually worth

"Your site is slow" is a weak argument because it has no denomination. Here is how to turn it into one, using numbers you already have.

The arithmetic

Open GA4 and find your monthly sessions, your conversion rate and your average order or lead value. The broadly replicated finding across large-scale studies is that each additional second of load time costs somewhere around 7% of conversions. You don't need to trust the exact figure — run it at 4% and it usually still makes the case.

A site with 20,000 monthly sessions, a 2% conversion rate and a $400 average value produces $160,000 a month. Take it from 5 seconds to 2 and, at a conservative 4% per second, you are looking at roughly a 12% lift — about $19,000 a month, from changing nothing about the marketing.

The four usual culprits

In the builds we audit, the delay is nearly always one of four things. Page-builder CSS that loads every widget stylesheet whether or not the page uses them — frequently 800 KB or more. Uncompressed hero images served at desktop dimensions to phones. Render-blocking JavaScript in the head. And a plugin stack where each addition costs 40 milliseconds and nobody has counted them in three years.

None of these are difficult. They are simply nobody's job, which is why they persist for years on sites that are otherwise well looked after.

What good looks like

Largest Contentful Paint under 2.5 seconds on a throttled 4G connection. Cumulative Layout Shift under 0.1. Total transferred weight under 1 MB for a marketing page. Those are not aspirational numbers — they are the threshold at which the page stops actively costing you traffic.

Measure yours on PageSpeed Insights, on mobile, not on the office wifi with a warm cache. The number you get there is the one your customers experience.