The data on load time and conversion rate is unambiguous. Here’s what we see in audits, and what to fix first
The numbers are not ambiguous
The relationship between page load time and conversion rate has been studied extensively. The findings are consistent across industries, page types, and device categories:
>image
These figures come from Google’s own research and have been replicated across multiple large-scale studies. The relationship is not linear — the biggest drop happens in the 0–3 second window, and particularly between 1 and 2 seconds. A page that loads in 1 second converts significantly better than a page that loads in 2 seconds, even though both feel “fast.”
What we see in audits
In a typical audit, we find performance issues in three categories:
Category 1: Image problems (present in ~90% of audits)
Uncompressed images, wrong format (JPEG where WebP or AVIF would be 30–50% smaller), wrong size (serving a 2000px image when the container is 400px), and missing lazy loading. Images are the single biggest page weight contributor on most sites and the easiest to fix.
Category 2: Render-blocking resources (present in ~70% of audits)
Scripts and stylesheets that block the browser from rendering the page until they’ve finished loading. Google Fonts loaded via a standard link tag, third-party chat widgets, marketing scripts loaded synchronously in the <head> — all of these delay the moment the user sees anything on the screen.
Category 3: Server response time (present in ~50% of audits)
Time to First Byte (TTFB) — the time from request to first byte of response — is often high because of shared hosting, unoptimised WordPress configurations, or lack of server-side caching. A site hosted on a slow server will never score well on Core Web Vitals regardless of what else is optimised.
The five fixes with the highest impact
Fix 1: Convert all images to WebP or AVIF
WebP is 25–35% smaller than JPEG at equivalent quality. AVIF is 50% smaller. Both are supported by all modern browsers. For WordPress, ShortPixel or Imagify will convert and serve automatically. This is the single highest-impact fix for most sites.
Fix 2: Implement proper caching
Server-side page caching means that returning visitors (and Googlebot) get a pre-built HTML file rather than a freshly generated page. On WordPress, this means a caching plugin (WP Rocket, FlyingPress, LiteSpeed Cache). Combined with a CDN like Cloudflare, this can reduce TTFB from 800ms to under 100ms.
Fix 3: Self-host and preload fonts
Loading fonts from Google Fonts adds a DNS lookup and a round trip to Google’s servers before your fonts can load. Self-hosting eliminates the DNS lookup. Adding a preload hint ensures the font starts loading as early as possible. This typically improves LCP (Largest Contentful Paint) by 200–400ms.
Fix 4: Defer non-critical JavaScript
Marketing scripts (chat widgets, tracking pixels, A/B testing tools) are often loaded synchronously, blocking page rendering. Adding defer or async attributes, or loading them via Tag Manager with appropriate triggers, means they load after the main page content. This improves both LCP and INP (Interaction to Next Paint).
Fix 5: Set explicit dimensions on all images and media
CLS (Cumulative Layout Shift) — the score that measures how much the page jumps around as it loads — is often caused by images without explicit width and height attributes. The browser doesn’t know how much space to reserve until the image loads, so the layout shifts. Adding dimensions to all images is a five-minute fix that can meaningfully improve CLS.
How to measure your current performance
Three tools, five minutes:
- PageSpeed Insights (pagespeed.web.dev) — run your homepage URL and get both mobile and desktop scores with specific improvement opportunities
- GTmetrix (gtmetrix.com) — run a waterfall report to see which specific resources are taking the longest to load
- Chrome DevTools → Lighthouse — run a local audit that isn’t affected by CDN caching, for a more accurate picture of raw performance
Target scores: 90+ on mobile in PageSpeed Insights, LCP under 2.0 seconds, CLS under 0.05, INP under 150ms.
A 1-second improvement in page load time can increase mobile conversions by up to 27% — Google/Deloitte, 2018. The study is from 2018. The finding is more true today than it was then.
Text: A performance audit will tell you exactly what's slowing your site down and what fixing it is worth in conversion terms.
Button: Book a Discovery Call → /contact/
