Why Page Speed Matters for Sales – and How to Measure It
by Stipe Kakic on Oct 15, 2026
Page speed matters because every visitor who gives up waiting is a visitor you paid for, directly through ads or indirectly through SEO work, who never gets the chance to buy. A slow site also tends to frustrate the people who do stay, especially on mobile. The good news: you can measure speed for free in a few minutes, and the most common problems have well-known fixes.
How a slow site costs you money
Speed affects your sales in several ways at once:
- Visitors leave before the page loads. Especially on mobile data, people won't wait long for a blank screen.
- Frustration lowers conversion. Buttons that react slowly or content that jumps around make people hesitate or misclick.
- Your ads get less efficient. Google Ads considers landing page experience in Quality Score. A poor experience can mean paying more per click.
- SEO. Google uses page experience signals, including Core Web Vitals, as part of its ranking systems. It is not the most important factor, but it can matter when competing pages are otherwise similar.
A worked example
Illustrative numbers for a small webshop:
| Before | After speeding up | |
|---|---|---|
| Paid visitors per month | 4,000 | 4,000 |
| Ad cost per month | 20,000 kr | 20,000 kr |
| Conversion rate | 1.5% | 1.8% |
| Orders | 60 | 72 |
| Ad cost per order | 333 kr | 278 kr |
This is not a promise of what speed work will do, just a way to see why even a small lift in conversion rate matters when you're paying for every visitor. You can plug your own numbers into my ROAS calculator to see what a change in conversion rate means for you.
How to measure page speed
There are two types of data, and it helps to know the difference:
- Field data (real users): how fast your site actually is for real visitors, collected by Chrome. This is what Google uses for Core Web Vitals.
- Lab data (a simulated test): a single test under fixed conditions. Great for finding problems, but it can vary between runs.
Tools I use
- PageSpeed Insights (free, from Google). Enter a URL and you get both field data (if your site has enough traffic) and a lab test with suggestions. Test your homepage, a key product or service page and your most common landing page from ads.
- Google Search Console. The Core Web Vitals report groups your URLs into good, needs improvement and poor, based on real user data.
- Lighthouse in Chrome DevTools. Useful for developers testing changes before they go live.
- Your own phone. Open your site on mobile data, not wifi. It's unscientific, but it shows what your customers experience.
Which numbers to look at
Don't obsess over the overall score out of 100. It's a lab summary and can swing between tests. Focus on the three Core Web Vitals:
- Largest Contentful Paint (LCP): how fast the main content appears. Google's "good" threshold is 2.5 seconds or less.
- Interaction to Next Paint (INP): how quickly the page responds when someone taps or clicks. Good is 200 milliseconds or less.
- Cumulative Layout Shift (CLS): how much things jump around while loading. Good is 0.1 or less.
The most common culprits
- Large images uploaded straight from a camera or phone. Resize and use modern formats like WebP.
- Too many apps or plugins, each adding scripts. Common on Shopify and WordPress.
- Third-party scripts: chat widgets, review widgets, multiple tracking tags, video embeds.
- Heavy themes with sliders, animations and large fonts.
- Slow hosting (mostly a WordPress issue; Shopify handles hosting for you).
What to fix first
- Compress and resize images, especially the large hero image at the top of the page.
- Remove apps, plugins and scripts you don't actually use. Uninstalling an app doesn't always remove its code, so check the theme too.
- Load tracking tags through Google Tag Manager rather than many hard-coded snippets, and remove duplicate tags.
- Replace autoplay videos and sliders with a single static image where possible.
- Set fixed dimensions for images and banners to reduce layout shift.
Measure before and after each change so you know what helped.
Key takeaways
- Speed affects conversion rate, ad costs and SEO at the same time.
- Use PageSpeed Insights and Search Console; prefer real-user data over a single lab score.
- Focus on LCP, INP and CLS rather than the overall score.
- Images, apps and third-party scripts are the usual suspects.
For a quick starting point, run my free website health check. If you want the fixes done for you, I do speed optimisation as part of web development for Shopify and WordPress sites.
Is your site slowing down your sales? Request a free review and I will tell you what's worth fixing first.