Website Carbon Calculator
Estimate the CO₂ emissions of a web page from its size and monthly visits, using the Sustainable Web Design model — and see the impact of making it lighter.
How to use
- 1Enter the page weight (check your browser DevTools Network tab, 'transferred') and monthly page views.
- 2Adjust the share of returning visitors (cached) and grid intensity if you know them.
How it's calculated
Sustainable Web Design model (v3): energy ≈ 0.81 kWh per GB transferred; returning visitors load ~2% of the data. CO₂ = energy × grid intensity (global average ≈ 442 g/kWh).
Frequently asked questions
What's a typical page weight?
The median web page is around 2–2.5 MB on desktop (HTTP Archive). Images and JavaScript are usually the biggest parts.
How can I reduce my page's footprint?
Compress and resize images (WebP/AVIF), remove unused JavaScript, cache well, and use a host powered by renewable energy.
How accurate is this?
It's a model with wide uncertainty, useful for comparing pages and tracking improvements rather than exact carbon accounting.