Page speed test: Core Web Vitals and what slowness costs you
Google loads your page on a phone and a desktop, we add real-user Chrome data, explain what to fix in plain language — and estimate how much revenue slow loading costs you each month.
Try:
- Asking Google to load your page on a mid-range phone
- … and on a desktop
- Reading real-user data (Chrome UX Report)
- Translating findings into business terms
This usually takes 15–40 seconds — Google loads your page for real.
We’ll run the test and email you the report
Leave your e-mail — an engineer runs the test as soon as the quota frees up and sends you the full report with the action plan.
Real users (last 28 days)
Chrome UX Report: how the page loaded for real Chrome visitors, 75th percentile. Google uses these numbers, not the lab score, for Core Web Vitals.
Lab test
One simulated load: a mid-range phone on a slow 4G connection, and a desktop on cable.
| Metric | Mobile | Desktop |
|---|
What your mobile visitor sees
Frames from the mobile test, from the first request to a complete page.
What makes up your LCP
Your largest element on mobile and where the time to show it goes.
Top issues
Ranked by how much each one delays the page for real people. The first three are free; the full list, resources and the action plan come with the report.
Action plan
Grouped by effort so you can start with what pays back fastest.
More pages
Test up to 3 more pages of the same site — a product page, a category, a landing page. Mobile only.
| Page | Score | LCP | Top issue |
|---|
Full report & action plan
All issues with developer instructions and the files to fix, a three-step action plan, the low / base / high revenue range and a check of up to 3 more pages. Sent as a PDF.
What slow loading costs you
Enter your own numbers — the calculation runs in your browser and nothing is sent anywhere. It works before the test finishes, too.
Based on example inputs — replace them with your numbers
Desktop traffic is not included — research shows a weaker, inconsistent link there.
This is an estimate, not a forecast. It applies a published A/B result (Vodafone, 2021: 31% faster LCP → 8% more sales) to your own numbers, capped at 35%. Your real effect depends on your audience, design and checkout.
How we calculate this
We take your monthly mobile revenue (sessions × mobile share × conversion × order value) and the relative LCP improvement from your current value to the target, capped at 80%. We apply the only causal result we know for LCP — Vodafone’s A/B test, 8% more sales for 31% faster LCP, an elasticity of 0.258 — and show a range of ×0.5 / ×1 / ×2 around it. The uplift is capped at 35% even for very slow sites. Desktop traffic is not included — research shows a weaker, inconsistent link there. Slow reactions (INP) and layout jumps (CLS) also cost conversions but are not turned into money: there is no comparable causal data.
What research says
- Vodafone, web.dev, 2021
An A/B test: the version with a 31% better LCP had 8% more sales, 15% better lead-to-visit and 11% better cart-to-visit rates.
web.dev - Deloitte, “Milliseconds Make Millions”, 2020
37 brands, ~30 million sessions: 0.1 s faster mobile sites saw +8.4% retail conversions and +9.2% order value; +10.1% travel conversions. A correlation study on mobile only — we show it as context and do not use it in the formula.
deloitte.com - Google / SOASTA, 2017 (cited by Deloitte)
As load time goes from 1 s to 3 s, the probability of a bounce rises by 32%; from 1 s to 5 s — by 90%.
deloitte.com - Portent, 2022
B2B sites that load in 1 second convert 3× better than sites that load in 5 seconds; e-commerce — 2.5× better. A comparison across sites, not proof of cause.
portent.com
Full report & action plan (PDF)
All issues with fixes and files, the action plan, the revenue range and the methodology — to your inbox, ready to forward to your developer or management.
Get a speed-up plan with a fixed-price estimate
An engineer reviews your report, tells you what is worth fixing first and sends a plan with a fixed price. No obligation.
- Front-end, back-end and hosting in one team
- Next.js, e-commerce platforms, technical SEO
- You keep the report even if you fix it yourself
How it works
- 1
Google Lighthouse
Google loads your page twice — on an emulated mid-range phone with slow 4G and on a desktop — and measures how fast it shows and responds.
- 2
Chrome UX Report
We add what real Chrome users experienced on this page (or the whole site) over the last 28 days — the data Google uses for Core Web Vitals.
- 3
Business translation
We rank the issues by impact, explain each one in plain language with who fixes it and how much work it is, and estimate what slowness costs you.
The lab score moves by a few points between runs — the network and Google’s servers are never exactly the same. Look at the trend and the real-user data, not at a single point.
FAQ
What are Core Web Vitals and what counts as “good”?
Core Web Vitals are three Google metrics of real user experience: Largest Contentful Paint (LCP) — when the main content appears, good at 2.5 s or less, poor above 4 s; Interaction to Next Paint (INP) — how fast the page reacts to taps and clicks, good at 200 ms or less, poor above 500 ms; Cumulative Layout Shift (CLS) — how much content jumps, good at 0.1 or less, poor above 0.25. A page passes when 75% of visits are “good” on all three. We also show First Contentful Paint (good ≤ 1.8 s) and Time to First Byte (good ≤ 0.8 s).
Why is my lab score different from real-user data?
The lab test is one simulated load on a mid-range phone with a slow connection and an empty cache. Real users have faster or slower phones, warm caches and different networks. Lab data is best for finding causes; real-user data shows what your visitors actually get — and that is what Google uses.
Why does my score change every time I run the test?
Lighthouse scores vary by a few points between runs because of network conditions, server load and third-party scripts that respond differently each time. Results are cached for 6 hours so that you can share a stable link; “Re-test now” runs a fresh test.
It says “not enough real-user data” — what does that mean?
The Chrome UX Report only includes pages and sites with enough Chrome visitors over the last 28 days. Smaller sites often have no data — that is normal. In that case we fall back to the data for the whole site, and if there is none, to the lab test, and say so next to every number.
How do you estimate the revenue I’m losing? Is it accurate?
It is an estimate, not a forecast. We apply Vodafone’s published A/B result (31% faster LCP → 8% more sales) to your mobile revenue and the gap between your LCP and the target, show a range of half to double that effect, and cap the uplift at 35%. Desktop, INP and CLS are not turned into money. The full method and the four sources are on the page and in the PDF.
Do Core Web Vitals affect Google rankings?
They are part of Google’s page experience signals, but relevance and content quality matter far more. Fast pages rarely win on speed alone; slow pages lose visitors before they ever read the content. We do not promise ranking changes — we show what speed costs you in conversions.
How is this different from PageSpeed Insights, GTmetrix or Pingdom?
The measurements are the same Google data as in PageSpeed Insights. What we add: issues explained in business language with who fixes them and how much work it is, an estimate of lost revenue with sources, an action plan grouped by effort, a PDF you can forward, and four languages.
How long does it take to fix, and what does it cost?
Quick wins — images, caching, render-blocking files, fonts — usually take hours to a couple of days. Heavy JavaScript, third-party tags and server rendering are sprint work. Re-architecting a single-page app is an engineering project of several weeks. After reviewing your report we give a fixed-price estimate.
Do you store my URL or data?
The tested URL and its result are kept in a cache for 6 hours so that repeat views and shared links load instantly. We do not store your calculator inputs — they stay in your browser and in the share link. Your e-mail and phone reach us only if you send one of the forms.