Blog · 5 min read ·
Website Speed and Conversions: A Core Web Vitals Guide
Direct answer: A slow page can lose a visitor before your content appears. Google's Core Web Vitals targets are LCP of 2.5 seconds or better, INP of 200 ms or better and CLS of 0.1 or better, judged at the 75th percentile of page loads for mobile and desktop separately.
The three Core Web Vitals
Three metrics tell you whether a page loads quickly, reacts quickly and stays still while loading. Google measures them on real visits, and the targets below come from web.dev's Core Web Vitals guide.
| Metric | What it measures | Good target | Common causes of a poor score |
|---|---|---|---|
| LCP (Largest Contentful Paint) | How long the largest visible element takes to appear | 2.5 seconds or better | Heavy hero images, slow server, render-blocking CSS or JavaScript |
| INP (Interaction to Next Paint) | How fast the page responds to taps, clicks and key presses | 200 ms or better | Long JavaScript tasks, heavy event handlers, many third-party scripts |
| CLS (Cumulative Layout Shift) | How much the layout jumps while loading | 0.1 or better | Images or embeds without reserved space, late-loading fonts, injected banners |
"75th percentile" means that three out of four visits should meet the target. Your fastest visitors on a good connection do not count for much. The slower quarter does.
How to measure for free
You do not need paid tools for a first look. Enter your address in PageSpeed Insights to see how real visitors experience the page and where it falls short. Lighthouse is Google's open-source tool for auditing performance, accessibility, SEO and more, and you can run it in Chrome.
The two kinds of data answer different questions:
- Lab data is a test load on a fixed device and network. Use it to check whether a specific change helped.
- Field data comes from real visitors on many devices and connections. Use it to see what customers actually get.
When the two disagree, trust field data for the verdict and lab data for debugging.
Seven fixes that usually come first
These tend to help without a rebuild:
- Compress and resize images. Keep them close to the size they are displayed at.
- Reserve space for images, ads and embeds. Set width and height so the layout does not jump.
- Prioritise the largest element. Make sure the main image or heading loads first.
- Defer scripts you do not need straight away. Fewer blocking scripts help both LCP and INP.
- Break up long JavaScript tasks. Shorter tasks keep the page responsive.
- Improve server response and caching. A fast server helps every other fix.
- Review third-party tags. Remove what you do not use and load the rest later.
If your team has no time for this, our fix and care service can do selected items from a written list.
Speed is one part of the funnel
A fast page with a confusing offer still loses the sale. A slow page may lose the visitor before they see the offer at all. How much speed matters depends on your traffic, your page type and your audience, so we do not quote a "seconds lost equals sales lost" figure. Nobody can honestly give you one without your own data.
That is why speed sits next to measurement and conversion in our audit. See our services overview for how the pieces fit.
What our audit and Quick Fix Pack cover
The audit scores six areas: conversion and sales funnel, SEO and AI-search visibility, security, speed, legal and privacy, and measurement. You get area scores, an overall score, a P0 to P3 priority list, a PDF and a CSV. The checks are passive and permitted: no penetration test, no code review and no legal opinion. A person reviews every finding.
| Audit | Price | Delivery | Scope |
|---|---|---|---|
| S | $490 | 5 business days | Up to 10 pages or screens, or 1 app flow; 30-minute walkthrough; 1 re-scoring within 30 days |
| M | $890 | 8 business days | Up to 30 pages or screens, or 2 app flows; plus comparison with 2 competitor sites |
| L | $1,690 | 12 business days | Up to 100 pages or screens, or 4 app flows (sampled); up to 2 languages |
The Quick Fix Pack needs an audit first. We pick items in writing from the P0 and P1 list, make a backup with a rollback note, go live only with your approval, and give you a change log with before and after measurements.
- S, $590: 5 business days, up to 5 items
- M, $990: 8 business days, up to 10 items
- L, $1,790: 15 business days, up to 20 items plus a full re-scoring
If you order fixes within 30 days of the audit, the audit fee is credited against the fix invoice, up to 50% of the fix price. See the audit report page for details. Prices are excl. VAT.
Limits
Passing all three thresholds does not promise higher rankings, traffic or sales. Search engines use many signals, and buyers care about price, trust and timing too. We can remove a technical barrier. We cannot promise what happens next.
FAQ
What are the Core Web Vitals thresholds?
LCP 2.5 seconds or better, INP 200 ms or better and CLS 0.1 or better, at the 75th percentile of page loads, for mobile and desktop separately.
How do I check my speed for free?
Use PageSpeed Insights for a quick view, or run Lighthouse in Chrome.
Why do lab and field results differ?
Lab data is one simulated load. Field data is real visits on many devices and networks.
Do I need an audit before the Quick Fix Pack?
Yes. The pack fixes items you choose in writing from the audit's P0 and P1 list.
Will better Core Web Vitals bring more sales?
Not by promise. They remove one common obstacle, but sales also depend on your offer, price and trust.