Website carbon calculator: how green is your site?
Enter any URL to estimate your website's carbon footprint per page view, see a page weight breakdown, and get tips to make your site greener and faster.
We fetch and analyze your page's HTML to estimate carbon footprint. No data is stored.
How the carbon calculation works
When you enter a URL, our scanner fetches the page HTML from edge servers and counts every resource tag - scripts, stylesheets, images, videos, and fonts. Each resource type is assigned a conservative average size to estimate total data transfer per page view.
The carbon formula is: CO₂ = data transfer (GB) × 0.81 kWh/GB × 442 gCO₂/kWh. We account for returning visitors who benefit from browser caching, using a 75/25 new-to-returning visitor split.
Website carbon benchmarks
| Grade | CO₂ per page view | What it means |
|---|---|---|
| A | < 0.2g | Cleaner than ~90% of websites |
| B | 0.2 – 0.5g | Cleaner than average |
| C | 0.5 – 1.0g | Average - room for improvement |
| D | 1.0 – 2.0g | Heavier than most |
| F | > 2.0g | Very heavy - significant optimization needed |
What we check and why
Page Weight (40%)
Total estimated size, image count, script count, and video usage. Heavier pages transfer more data and consume more energy.
Efficiency (35%)
Modern image formats (WebP/AVIF), font optimization, and lazy loading. These reduce data transfer without changing content.
Green Hosting (25%)
Whether your site is hosted on a platform with renewable energy commitments (Cloudflare, Vercel, Netlify, Google Cloud, AWS).
The top 3 fixes for a greener website
1. Optimize images.
Images are typically 50-70% of total page weight. Converting
from JPEG/PNG to WebP or AVIF reduces file size by 25-50% with
no visible quality loss. Add loading="lazy" to
below-fold images to defer loading until needed.
2. Reduce JavaScript. JavaScript is the most expensive resource per byte - it must be downloaded, parsed, compiled, and executed. Audit third-party scripts (analytics, chat widgets, tag managers) and remove anything not essential.
3. Choose green hosting. The energy source powering your server matters. Hosting on a provider with renewable energy commitments (Cloudflare, Vercel, Google Cloud) can reduce the carbon intensity of every page view by up to 80%.
Frequently asked questions
- How is website carbon footprint calculated?
- We estimate total data transfer per page view by analyzing the HTML and counting resources. Then we apply the formula: CO₂ = data transfer (GB) × 0.81 kWh/GB × 442 gCO₂/kWh. We account for returning visitors who benefit from browser caching.
- What is a good CO₂ per page view?
- Under 0.2 grams is excellent. Under 0.5 grams is good. Between 0.5 and 1.0 grams is average. Over 1 gram means your page is heavier than most and has significant optimization opportunities.
- How do I reduce my website's carbon footprint?
- Optimize images (WebP/AVIF), reduce JavaScript, enable lazy loading, use green hosting, and enable caching. These changes also improve page speed and SEO.
- Does website carbon footprint affect SEO?
- Indirectly - the same factors that increase carbon also slow your site, and Google uses page speed as a ranking factor. A lighter, greener site typically ranks better.
- What is green hosting?
- Hosting providers using renewable energy or carbon offsets. Cloudflare, Vercel, Google Cloud, and AWS have renewable energy commitments.
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