How Website Speed Affects Your Conversions (And What To Do About It)

Website speed is one of those improvements that business owners often treat as a technical nicety rather than a commercial priority. Google's own data shows that a one-second delay in mobile page load time reduces conversions by up to 20 percent. For a business converting 2 percent of website visitors at 1,000 visitors per month, a one-second improvement in load time could mean an additional four enquiries per month. Compounded over a year, that is a meaningful number.

What page speed actually means

Page speed is not a single measurement, it is a collection of metrics that Google groups under the term Core Web Vitals. The three that matter most are:

Largest Contentful Paint (LCP): how long it takes for the largest visible element on the page to load. Under 2.5 seconds is good. Over 4 seconds is poor. This is what most users experience as the page loading.

First Input Delay (FID) / Interaction to Next Paint (INP): how responsive the page is to user interaction. Poor interactivity makes a page feel broken or unfinished even if it has loaded visually.

Cumulative Layout Shift (CLS): how much the page layout moves around while loading. A button that shifts down as an image loads and causes an accidental click is a CLS problem. It is one of the most frustrating user experiences and one of the most common.

Google uses these metrics as ranking signals. Pages that perform well on Core Web Vitals receive a boost in search rankings. Pages that perform poorly are penalised relative to faster competitors.

The most common causes of slow websites

Images are the most common cause of slow websites for small businesses. An unoptimised image from a phone camera might be 4 to 8 megabytes. The same image properly compressed and resized for web use might be 80 to 200 kilobytes. The difference in load time is enormous.

Hosting quality has a significant impact that many businesses underestimate. Budget shared hosting from low-cost providers can add 500 milliseconds to 2 seconds of load time compared to better hosting. For businesses where site speed matters commercially, paying an extra £20 to £50 per month for better hosting pays for itself immediately.

Third-party scripts, chat widgets, analytics tools, social media embeds, advertising pixels, each add load time. A website with ten third-party scripts loading on every page is fighting a losing battle on speed regardless of how optimised the core site is.

WordPress with poorly chosen plugins is one of the most common causes of slow small business websites in the UK. A WordPress site with 30 plugins, a heavy page builder and shared hosting will almost never achieve good Core Web Vitals scores regardless of how much time is spent on other optimisations.

Quick wins that make the biggest difference

Compress and resize your images. Every image on your website should be compressed using a tool like Squoosh or TinyPNG before upload. Images should be no wider than they need to be, a 1200 pixel wide image for a thumbnail that displays at 300 pixels wide is wasting three-quarters of the file size.

Enable caching. Caching stores a version of your pages so they do not need to be rebuilt from the database on every visit. Most website platforms have caching available as a setting or plugin. This is one of the highest-impact and lowest-effort improvements available.

Remove unnecessary plugins and scripts. Audit every third-party script running on your site. If a chat widget is generating zero conversations per month, remove it. If you have both Google Analytics and another analytics tool tracking the same thing, remove one.

Switch to a modern image format. WebP images are significantly smaller than JPEG or PNG at equivalent quality. Most modern browsers support WebP and most website platforms can serve WebP automatically.

How to measure your current speed

Google PageSpeed Insights (pagespeed.web.dev) is the definitive tool for measuring Core Web Vitals. Enter your URL and you receive a score out of 100 for both mobile and desktop, along with specific recommendations for improvement.

The mobile score is the one that matters most, both for Google ranking purposes and because the majority of website visitors for most UK small businesses now come from mobile devices.

A score above 90 on mobile is excellent. Between 70 and 90 is acceptable. Below 70 indicates significant performance issues that are likely affecting both rankings and conversions. Below 50 is a serious problem that warrants either significant technical work or considering rebuilding on a faster platform.