Core Web Vitals: What a Slow Website Costs in Sales and Inquiries
A slow site costs sales and inquiries. See what Core Web Vitals measure, what a Vodafone test showed, and how to calculate the cost to your own business.
Published on 5 min readTopics:Core Web Vitalstechnical SEOwebsite speed
Every visit that lands on a slow page is a click you paid for or earned that may never become a sale or an inquiry. Google measures that experience with three indicators, the Core Web Vitals, and a public test by Vodafone showed how much sales changed when they improved. This article explains the three in plain English, shows how to calculate what a slow website costs your business, and says what to ask your team for first.
Core Web Vitals: the three measures Google applies to your site's pages
They are three measures of what a visitor feels when using the page, each with a threshold published by Google:
- Loading (LCP): the largest element on the screen, such as the main photo or the headline, should appear within 2.5 seconds.
- Response to a tap (INP): after a click or tap, the page should react within 200 milliseconds.
- Stability (CLS): the page should not jump around while loading, with a score of 0.1 or lower. The higher the score, the worse it is: it rises when a button or a block of text moves in the middle of reading.
Google considers a page as passing when all three measures fall within the threshold for at least 75% of visits, with mobile and desktop measured separately. Passing two and failing one counts as failing.
Google's documentation recommends that every site owner reach good results on all three, and says this aligns with what its ranking systems seek to reward. It does not promise a position. The effect you can measure most clearly is on sales, and that is the subject of the next section.
What a faster site changes in sales: the Vodafone test
Vodafone, a telecommunications operator present in Europe and Africa, ran an A/B test (two versions of a page shown to equal audiences) on a campaign page. The two versions were identical in look and function. The only difference: one had been tuned for the measures above, with LCP 31% better as measured on real visits. The traffic, which came from paid media, was split evenly between them.
The result, published by Google in 2021: 8% more sales, 15% more visitors who became a sales lead, and 11% more visitors who reached the cart.
The changes were in images (the main one was resized, and the ones not yet in view stopped loading up front) and in code that delayed the page from showing.
That is the result of one company, on one page, with paid traffic. Yours may differ. The test is a reason to measure your own site, not a forecast.
Do the math on what your slow site costs
Start with what passes through the site today: visits per month × purchase (or inquiry) rate × average order value. Run it only for the pages that sell or capture inquiries, not for the whole site.
An example, with illustrative numbers: 50,000 visits per month, 2% buy, average order of $400. That is 1,000 orders and $400,000 a month. If a speed improvement gave 8% more sales, as in the Vodafone test, that would be 80 more orders and $32,000 more per month.
If you capture inquiries, the math is the same: 1% of 50,000 visits is 500 inquiries a month, and a 15% gain would be 75 more. The 8% and the 15% come from one company's test; they are not a promise for your site.
Swap in your own numbers and also try smaller gains, like 2% and 4%. If the fix pays off in the modest scenario, the decision is easy.
Where to see your Core Web Vitals today, without coding
PageSpeed Insights and the Core Web Vitals report in Search Console (Google's tool for site owners), both free, use data from real visits collected by the Chrome browser. It is the measure closest to what your customer feels.
Look at mobile and desktop separately, and go beyond the homepage: check the product page, the contact form, and the cart. A test run on the spot and real-visit data can diverge, and the second is the one to decide on.
To audit the rest of the technical base, such as indexing (whether Google knows all your pages) and the site map, follow the technical SEO checklist.
Three requests to make of your team or vendor
- The LCP, INP, and CLS numbers for the three pages that sell or capture the most inquiries, on mobile, with the measurement date.
- For each page outside the threshold, what slows it down (a heavy image, code that holds back the display, an element that jumps), how long the fix takes, and what it costs.
- A before-and-after measurement, on the same page and over the same period, looking at sales and inquiries, not just the score. Change one thing at a time; it is the method of conversion rate optimization.
If anyone answers "I don't know" to request 1, that is the first job. Without a starting number, no later gain can be proven.
Know which page to start with and what it is worth
With the measures and the math in hand, you decide where to invest first and how much each fix can return in sales and inquiries.
We read the Core Web Vitals of the pages that sell the most on your site, calculate what each one costs, and hand you the list of what to fix first. Reach us on WhatsApp or write to contato@ygormendanha.com.
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