How Fast Should Your Website Be? A Plain-English Guide to Core Web Vitals

If you've ever run your website through a speed test and gotten back a wall of red numbers and acronyms, you're not alone. Google measures site performance with something called Core Web Vitals, and the results can feel like they're written for engineers, not business owners.

Here's the plain-English version: what these numbers mean, what scores you should actually care about, and what's usually behind a slow site.

Why This Matters at All

Two reasons.

First, people leave slow sites. The data on this is consistent and brutal — every additional second of load time costs you visitors before they've seen a single word of your content. For a business that spends money driving traffic to its site, a slow site is a leak in the bucket.

Second, Google uses page speed as a ranking factor. It has said so directly. Core Web Vitals are part of how Google decides where you land in search results. A slow site doesn't just frustrate the visitors you have — it costs you the visitors you could have had.

The Three Numbers

Core Web Vitals come down to three measurements. That's it.

Largest Contentful Paint (LCP) — how long until the main content of the page appears. This is the "is anything happening yet?" metric. Aim for under 2.5 seconds. Over 4 seconds is a problem.

Interaction to Next Paint (INP) — how quickly the page responds when someone clicks, taps, or types. This is the "did that button do anything?" metric. Aim for under 200 milliseconds. Over 500ms feels sluggish.

Cumulative Layout Shift (CLS) — how much the page jumps around as it loads. You've felt this: you go to tap a link, an image loads above it, and suddenly you've tapped something else. Aim for under 0.1. This one is measured as a score, not a time.

You don't need to memorize these. You need to know that a good site loads fast, responds instantly, and doesn't jump around. The numbers just put a grade on those three things.

How to Check Your Own Site

Google's PageSpeed Insights is free and the most direct way to see your scores. Type in your URL and it gives you results for both mobile and desktop, plus specific recommendations.

Check mobile first. Most of your traffic is probably on phones, and mobile is almost always the worse score. A site that scores well on desktop and poorly on mobile is a site that's failing most of its visitors.

One thing worth understanding: PageSpeed Insights shows you two kinds of data. "Lab" data is a simulated test run on the spot. "Field" data is real measurements from actual visitors over the past month — that's the one Google actually uses for ranking. If your field data is missing, your site probably doesn't get enough traffic for Google to have collected it yet.

What Usually Causes a Slow Site

In our experience, slow sites are slow for a small number of predictable reasons:

Unoptimized images. This is the single most common cause, by a wide margin. A photographer hands over 5MB images, they get uploaded as-is, and now every page drags. Images should be compressed and sized for the web — a hero image doesn't need to be print resolution.

Too many scripts. Every tracking pixel, chat widget, popup tool, and analytics tag adds weight. Each one seems harmless. Twelve of them together are not.

Cheap or overloaded hosting. If your server is slow to respond, nothing else you do fully fixes it. Budget shared hosting is a common culprit, especially for WordPress sites.

No caching. Caching lets returning visitors load your site without rebuilding everything from scratch. Without it, every visit is starting from zero.

A bloated theme or page builder. Some WordPress themes and drag-and-drop builders load enormous amounts of code to render a simple page. The convenience comes at a real performance cost.

What's Realistic to Expect

Not every site needs a perfect score, and chasing 100/100 is usually a poor use of money. Here's a more honest framing:

• Above 90: Excellent. You're in good shape.
• 50 to 90: Typical, and usually improvable with straightforward fixes.
• Below 50: Something is meaningfully wrong, and it's likely costing you visitors and ranking.

If you're sitting below 50 on mobile, that's worth addressing. The good news is that the fixes are often the boring, fixable kind — compress the images, add caching, cut the scripts you don't need, upgrade the hosting. It's rarely a mystery.

The Bottom Line

You don't need to become a performance engineer. You need to know roughly where your site stands and whether it's costing you anything. Run PageSpeed Insights, look at your mobile score, and if it's bad, the cause is probably one of the handful of things listed above.

If you'd rather have someone diagnose it and fix it properly, we're happy to take a look. We'll tell you what's actually slowing your site down — and whether it's worth fixing.