Does Website Speed Affect Conversions? The Data Says Yes

Yes — and the data is unambiguous.

If your website takes more than 3 seconds to load on mobile, you're losing roughly half your visitors before they see a single line of content. This isn't theory. It's been measured at scale by Google, Amazon, Walmart, and dozens of independent researchers.

The relationship between page speed and conversions is one of the most thoroughly documented phenomena in web performance. Here's what the evidence shows — and what it means for your business.

What the Research Shows

These numbers come from different industries, different time periods, and different measurement methodologies — and they all point in the same direction.

Why Speed Affects Buying Decisions

It's partly psychology. A slow site signals something is wrong. Visitors don't consciously think "this site has poor infrastructure" — they just feel uneasy, and leave.

It's partly practical. Mobile users on 4G connections will simply close a tab that hasn't loaded in 3–4 seconds. They have other options — including your competitors.

And it's partly trust. Research from Google and Nielsen Norman Group consistently shows that perceived credibility drops with slower load times. If your site is slow, people are less likely to trust you with their data, their order, or their enquiry.

The Core Web Vitals Factor

Since 2021, Google uses a set of performance metrics called Core Web Vitals as a direct ranking signal. The three key measures:

• Largest Contentful Paint (LCP): how long until the main content is visible. Target: under 2.5 seconds.
• Interaction to Next Paint (INP): how quickly the page responds to clicks or taps. Target: under 200ms.
• Cumulative Layout Shift (CLS): how much the page jumps around while loading. Target: under 0.1.

Sites that score green on all three get a ranking boost in Google search results. Sites that fail get pushed down — and lose organic traffic as a result.

This creates a compounding problem: a slow site not only converts fewer visitors directly, it also attracts fewer visitors from Google in the first place.

How to Know If Speed Is Hurting You

The fastest way to check is Google PageSpeed Insights. Enter your URL and you get a score from 0 to 100, plus the specific metrics that are failing.

What to look for:

• Below 50 on mobile: serious problem. You're likely losing significant traffic and conversions.
• 50–70 on mobile: room for meaningful improvement. Optimisation or a rebuild could move the needle.
• 70+ on mobile: solid. You're not leaving obvious performance gains on the table.

Check mobile specifically. Desktop scores tend to be more forgiving because desktop connections and processors are faster. But the majority of web traffic — and the majority of Google's indexing — is mobile.

Why WordPress Sites Often Get Stuck

The most common pattern we see: a business owner has done everything right. Good hosting, caching plugin, CDN, image compression. But the mobile PageSpeed score is still stuck in the 40s or 50s.

This usually isn't a configuration problem — it's an architecture problem. WordPress generates pages by running PHP, querying a database, and executing a chain of plugins on every request. Caching helps, but there's a ceiling on how fast this architecture can go.

A site built with static generation — Next.js, for example — renders pages at build time and serves them as pre-built files from a CDN edge. There's nothing to execute. The file is already there, ready to deliver in under 100ms globally.

What You Can Actually Do

If you're scoring under 70 on mobile, the options are roughly:

• Switch to better hosting: moving from shared hosting to a managed provider (Kinsta, WP Engine) typically adds 5–15 points.
• Plugin audit: removing unused plugins reduces the PHP execution chain and can add 5–10 points.
• Image optimisation: converting to WebP/AVIF and lazy-loading offscreen images can add 5–20 points.
• Architectural change: if you've done the above and you're still below 70, you may be hitting the ceiling of what's achievable within your current platform. A rebuild in Next.js consistently moves sites to 90+.

The right fix depends on where you're starting from. A site at 58 can often reach 75–80 with configuration changes. A site at 38 that's already been optimised probably needs an architectural change.

The Business Case for a Rebuild

If your site currently converts at 2% and a rebuild pushes that to 2.5% — that's a 25% revenue increase from the same traffic. At any meaningful monthly revenue figure, that pays for a migration in weeks, not years.

The one-time cost of a Next.js migration ranges from €1,500 to €4,000 depending on site size. Most clients with active traffic break even within 6–12 months from conversion gains alone — before accounting for SEO improvements from better Core Web Vitals scores.

To see what your site currently scores and what's holding it back, get a free website health report at webvise.io/wp-health-report. It runs in 60 seconds. No signup required.