How much revenue does a slow website lose?

It depends on your traffic, but the research is consistent: slower pages convert fewer visitors. Deloitte found a 0.1 second faster mobile site lifted retail conversions by 8.4%, and Portent found ecommerce conversion rates fall from 3.05% at 1 second to 0.67% at 4 seconds. This checker uses a more cautious 10% fewer sales for each second over 2.5 seconds, which you can change.

How is the revenue loss worked out?

We take your load time (Largest Contentful Paint), find how many seconds it is over the 2.5 second target, and apply your sales lost per second for each one. Revenue at target = monthly revenue ÷ (1 − loss per second) to the power of the extra seconds. Revenue lost is the difference.

What is a good load time for an online store?

Google's target is a Largest Contentful Paint of 2.5 seconds or less for at least 75% of visits. Over 4 seconds is rated poor. Most shoppers are on mobile, so the mobile result matters most.

What is Largest Contentful Paint (LCP)?

LCP is the time it takes for the biggest thing on the screen, usually the hero image or main product photo, to appear. It is the closest single measure to when a page looks loaded, and it is one of Google's three Core Web Vitals.

Why is my mobile result slower than desktop?

Google tests mobile on a mid-range phone with a slower 4G connection, which is closer to how many shoppers browse. Large images, apps and scripts hurt far more on a phone than on a laptop with fast broadband.

Why does my speed score change between tests?

Each test loads the page fresh, so server load, ads, apps and network conditions shift the result a little each time. Real-visitor data from Chrome, shown when Google has enough of it, is steadier because it covers the last 28 days.

Does site speed affect SEO?

Yes, a little. Core Web Vitals are part of Google's page experience signals. The bigger effect is on sales: faster pages keep more visitors, convert more of them and make your ad spend go further.

How do I speed up a Shopify or WooCommerce store?

Start with the fixes the checker lists first. The usual wins are smaller, modern format images (WebP or AVIF), removing apps and scripts you no longer use, loading third-party code later, a lighter theme, and good hosting or a CDN.

Free tool

Free Site Speed Checker and Revenue Loss Calculator

Test how fast your store loads on mobile or desktop, then see how much revenue slow pages are costing you each month and what to fix first. No sign-up.

By Anthony McGrath · Updated 16 October 2026

Test your site

Optional tweaks: sales lost per second, target, your own load timeOptional

Leave these as they are for a quick answer, or set your own numbers.

Sales lost per extra second

10% is a cautious reading of the research.

Target load time

Google's "good" level is 2.5 seconds.

Or enter a load time yourself

Leave empty to use the test result.

Your results

Speed is measured by Google PageSpeed Insights. Up to 4 new tests every 5 minutes, 12 an hour and 30 a day per visitor; repeat tests of the same page within 6 hours are instant and free. Revenue figures are estimates for planning, based on the numbers you enter.

Free Site Speed Checker and Revenue Loss Calculator

Test your site

Your results

Speed details

What to fix first