How Cogworks' Website Carbon Calculator works

A complete way to measure your website's digital sustainability

This calculator is in BETA

The Website Carbon Calculator is in BETA. Cogworks continuously improves its accuracy and usefulness, aiming to provide a truly helpful and transparent tool for understanding website sustainability. Even in its development phase, this thorough approach gives you a realistic baseline of your site's performance and environmental and business impact, forming the foundation for informed, actionable insights. 🙌🌱💪 (Learn more about our methodology)

Our free Website Carbon Calculator is a comprehensive tool for understanding your website's digital sustainability score and what to do about it. It's designed to support your brand goals, turning website data into powerful insights to help your business and our planet thrive.

The calculator uses the Green Web Foundation's trusted CO2.js open-source library and advanced performance metrics. This means you get a complete digital sustainability score that includes your website's carbon footprint, performance metrics, and hosting analysis—not just emissions data. Take the insights and run, or let our sustainability experts work up your website.

Check Free Score

How our website carbon calculator shapes up

Not all carbon calculators are the same.

Many tools stop at basic page weight and data transfer estimates. Here's what makes ours slightly different.

Other calculators

✅ Estimate CO2 based on page size
❌ No performance analysis
❌ No hosting verification
❌ Generic recommendations

Our calculator

✅CO2.js verified carbon data
✅ Website performance analysis
✅ Green Web Foundation hosting check
✅ AI-powered specific fixes for your site

The technical details

What powers the carbon calculator and why

At the heart of our website's carbon calculator is the @tgwf/co2 library from The Green Web Foundation. This is a great base to start from. The framework is based on energy intensity research, network energy models, device power consumption and International Energy Agency data. Plus, the library is maintained with regular updates, as documented in their GitHub repository and release notes.

How our carbon calculator measures more than just carbon

The tech behind the advanced measurements

Performance metrics
We integrate Google PageSpeed Insights API data because performance directly affects energy consumption:

• Core Web Vitals: Loading speed impacts server processing time and energy use

• Resource optimisation scores: Inefficient code wastes computational power

• Caching effectiveness: Poor caching multiplies energy consumption

• JavaScript execution time: Long-running scripts drain device batteries
Green hosting verification
Our tools for measuring website carbon footprint verify renewable energy usage through:

• Real-time Green Web Foundation API checks

• Hosting provider renewable energy certifications

• Data centre location and regional energy mix

• Carbon offset program participation
Resource efficiency analysis
Beyond basic file sizes, we measure:

• Compression effectiveness: How well your content is optimised

• Unused code detection: Resources loaded but never used

• Image optimisation levels: Oversized images waste energy

• Third-party script impact: External resources affecting sustainability

How it works out your score

Page load times:

• Browser automation loads your page like a real visitor
• Every HTTP request is tracked and categorised
• Actual transferred bytes are measured (including compression)
• Multiple page loads ensure accuracy