What is Website Performance Score?
A website performance score grades your site across mobile responsiveness, page speed, SEO fundamentals, security, and accessibility. It identifies the specific technical issues that reduce conversions and search rankings.
The Formula
Performance Score = Sum of (Rule Weight × Pass/Fail) across 10 criteria
Each rule is weighted by its impact on user experience and SEO. Mobile and speed carry the highest weight.
Worked Example
A small business website is graded across 10 performance criteria.
- Mobile responsive: Pass (12 points)
- Page speed under 3 seconds: Fail (0 of 12 points)
- Meta title present: Pass (10 points)
- Meta description present: Pass (10 points)
- Heading hierarchy correct: Fail (0 of 10 points)
- SSL active: Pass (10 points)
- Images optimized: Fail (0 of 8 points)
- Alt text present: Pass (8 points)
- Clear CTA: Pass (10 points)
- Structured data: Fail (0 of 10 points)
📌 The site scores 60/100, passing on fundamentals but losing 40 points on speed, headings, images, and structured data. Fixing page speed alone could improve conversions by 7% per second saved.
Why This Matters
Conversions
Each second of page load delay reduces conversions by 7%, per Google research on mobile performance. A site scoring below 50 in PageSpeed Insights is likely losing half its potential leads to poor performance before visitors ever see the offer or the form.
Search Rankings
Google uses Core Web Vitals as ranking signals since the 2021 Page Experience update. Sites with better performance scores rank higher and receive more organic traffic, with Google Search Console data showing that pages passing Core Web Vitals thresholds receive a measurable impression share advantage over failing pages in competitive SERPs.
User Trust
Missing SSL, slow loading, and poor mobile experience make visitors leave immediately. According to Google and Deloitte research, 53% of mobile users abandon sites that take over 3 seconds to load, and sites without HTTPS receive a "Not Secure" browser warning that reduces form submission rates by an estimated 15-20% among first-time visitors.
Common Mistakes
❌ Ignoring mobile performance
Over 60% of web traffic is mobile according to StatCounter global data. Testing only on desktop misses the majority of your audience. Google Search Console data shows that 63% of Google searches originate from mobile devices, and sites with mobile performance scores below 50 in PageSpeed Insights receive 30% fewer organic impressions than equivalent desktop-first sites because Google uses mobile-first indexing.
❌ Uploading uncompressed images
Large images are the most common cause of slow page loads. Compress images and use modern formats like WebP. HTTP Archive analysis of 6 million web pages found that images account for 45% of total page weight on average, and converting JPEG and PNG files to WebP reduces file sizes by 25 to 35% with no perceptible quality loss, making image compression the single highest-impact performance fix for most small business sites.
❌ Skipping structured data
Structured data enables rich snippets in search results, increasing click-through rates by 20-30%. Google Search Central data shows that pages with structured data markup receive a 20% higher click-through rate on average than pages without it for equivalent ranking positions, because rich results with star ratings, breadcrumbs, or FAQ dropdowns occupy more visual space and signal trustworthiness before the user clicks.
Industry Benchmarks
| Category | Good | Average | Poor |
|---|---|---|---|
| Small Business Sites | 80-100 | 50-70 | Below 40 |
| Agency/SaaS Sites | 85-100 | 65-80 | Below 55 |
| Ecommerce Sites | 75-100 | 55-75 | Below 45 |
Source: Google Core Web Vitals Report and HTTP Archive Data
Benchmark data sourced from Google Core Web Vitals Report and HTTP Archive Data.