Performance Score Calculator
Calculate a Lighthouse-style performance score from your metrics and see what to fix first.
Performance score (mobile)
First Contentful Paint (10%)81
Speed Index (10%)78
Largest Contentful Paint (25%)67
Total Blocking Time (30%)63
Cumulative Layout Shift (25%)85
Your metrics
Fix these first
- Total Blocking Time: 450 ms → 200 ms would add about +8 points.Split long JavaScript tasks, remove unused JS, lazy-load third-party scripts and move work to web workers.
- Largest Contentful Paint: 3.4 s → 2.5 s would add about +6 points.Preload the hero image, serve it in AVIF/WebP at the right size, and speed up the server response (TTFB).
- Cumulative Layout Shift: 0.12 → 0.10 would add about +1 points.Give images and embeds width/height, reserve space for ads and banners, and avoid inserting content above existing content.
- Speed Index: 4.2 s → 3.4 s would add about +1 points.Show above-the-fold content sooner: defer non-critical scripts and reduce main-thread work.
- First Contentful Paint: 2.1 s → 1.8 s would add about +1 points.Cut render-blocking CSS/JS, inline critical CSS, use a CDN and preconnect to key origins.
Core Web Vitals
3.4 sLCP Needs improvement
240 msINP Needs improvement
0.12CLS Needs improvement
To pass, LCP ≤ 2.5 s, INP ≤ 200 ms and CLS ≤ 0.1 at the 75th percentile of real visits.
Page weight → load time
| Slow 4G (1.6 Mbps, 150 ms RTT) | ≈ 13.2 s |
|---|---|
| Fast 4G (9 Mbps, 60 ms RTT) | ≈ 2.7 s |
| Cable (50 Mbps, 20 ms RTT) | ≈ 0.6 s |
| Fibre (300 Mbps, 5 ms RTT) | ≈ 0.1 s |
A rough download-only estimate: real loads also depend on caching, compression, rendering and JavaScript execution.