How web performance (Core Web Vitals) affects your sales

A slow website loses customers before they read a single word. That is not an opinion: it is what Google measures with Core Web Vitals, three metrics that sum up how your site feels to the people using it. Here we explain them in business language, no jargon, and show you how to measure yours for free.

What Core Web Vitals are

Google documents three metrics it groups under the name Core Web Vitals. They measure concrete aspects of your visitors' real experience:

LCP — Largest Contentful Paint

The time it takes for the main element of the page to appear (usually the image or the big headline). In business terms: how long the customer waits until they see something useful. Google considers an LCP under 2.5 seconds good.

INP — Interaction to Next Paint

Measures how long the site takes to respond when the user clicks, types or taps. In plain terms: whether your site reacts instantly or feels sticky. It replaced the older FID in 2024, and Google recommends keeping it under 200 milliseconds.

CLS — Cumulative Layout Shift

Measures how much content moves while it loads. We have all gone to press a button when, suddenly, the page jumps and we tap the wrong thing. In plain terms: how much frustration your site causes without the user being able to name it. Google looks for a value under 0.1.

Why this affects your sales

Google consistently documents that as loading time increases, the likelihood of the user abandoning the page increases too. The business logic is simple: every second of waiting is an open door for the visitor to leave for a competitor who is one click away.

There are two ways performance touches your revenue:

1. Direct (conversion): a user who waits less and does not suffer content jumps completes more purchases, more forms and more calls. Technical friction turns into abandoned carts.
2. Indirect (ranking): Core Web Vitals are a ranking factor confirmed by Google. A faster site tends to rank better, which means more visits before conversion even enters the conversation.

We do not promise magic percentages because every business is different, but the direction is clear and documented: slower is worse.

How to measure your site for free

You do not need to hire anyone to find out where you stand. Use PageSpeed Insights (pagespeed.web.dev), Google's free tool:

1. Go to the site, paste your page URL and press "Analyze".
2. Look first at the field data section (real users over the last 28 days) if your site has traffic. That is what Google actually uses.
3. Below it you will see the lab data and a list of concrete improvement opportunities.
4. Repeat the analysis on mobile and desktop: mobile is almost always the one that suffers.

One tip: also analyse the pages that matter most (a product page, the contact page), not just the homepage. That is where sales are lost.

What to do with the results

If your metrics are in the red, the most common causes we find at InterHuge are:

• Unoptimised images: 4 MB photos where 200 KB would do. It is the number one problem and the easiest to fix.
• Too much JavaScript: third-party plugins and scripts (chats, banners, duplicate analytics) that block loading.
• No reserved space for images and ads: the classic cause of high CLS.
• Insufficient hosting: a slow server drags everything else down.

The first two usually deliver the biggest improvement for the least effort. You do not need to rebuild the site to gain a lot.

Frequently asked questions

How often should I measure my site?

A monthly check is enough for a stable site. If you have just published changes, installed a plugin or uploaded lots of photos, measure right after: those are the moments when performance breaks without warning.

Do Core Web Vitals matter more on mobile or desktop?

Google evaluates both, but for most local businesses mobile is where the bulk of traffic is and where the metrics come out worst. Prioritise mobile unless your audience is clearly desktop.

Will improving performance push me up on Google immediately?

It is not a switch. Core Web Vitals are one of several ranking factors; improving them helps, but content and site authority still weigh in. The most immediate gain is usually in conversion, not position.

Do I need to rebuild the site to fix the metrics?

Almost never. Optimising images, removing unnecessary scripts and reserving space for content solves most cases without touching the design.

Conclusion

Core Web Vitals are not a technical whim: they are the measure of how much patience you ask of each visitor. Start by measuring with PageSpeed Insights and prioritise images and scripts. If you would rather we review it and tell you exactly what is slowing your site, get in touch or see how we look after performance in every web design project.