Website Carbon Calculator (from Page Weight)
Estimate the CO2e per page view and per year of a web page from its transfer size, using the Sustainable Web Design Model v4, with green hosting and grid intensity.
Sustainable Web Design Model v4 (sustainablewebdesign.org): 0.194 kWh/GB operational and 0.106 kWh/GB embodied energy, split across data centres, networks and user devices.
This is a model estimate from transfer size, not a measurement of your servers. Rating bands are the SWD v4 digital carbon ratings.
| Segment | Operational kWh/GB | Embodied kWh/GB | Operational g | Embodied g | Total g |
|---|---|---|---|---|---|
| Data centres | 0.055 | 0.012 | 0.05434 | 0.01186 | 0.0662 |
| Networks | 0.059 | 0.013 | 0.05829 | 0.01284 | 0.07114 |
| User devices | 0.08 | 0.081 | 0.07904 | 0.08003 | 0.15907 |
Every page view uses electricity in a data centre, across the network and on the visitor's device, and making that equipment adds embodied emissions. This calculator estimates the carbon footprint of a web page from the one number you can measure yourself — how much data it transfers — using the Sustainable Web Design Model version 4, the method behind CO2.js and most website carbon tools. Enter your traffic to see the yearly total, and whether green hosting or caching changes it.
How to use this tool
- Open the page in Chrome or Firefox, open developer tools (F12), choose Network, tick "Disable cache" and reload.
- Enter the "transferred" total and its unit (DevTools uses kB = 1,000 bytes).
- Enter monthly page views and, if you know them, the share of returning visitors and how much of the page they have cached.
- Tick green hosting if your host is verified by the Green Web Foundation, and change the grid intensity if you have a figure for your country.
Formula
g per view = GB × [Σ operational kWh/GB × grid + Σ embodied kWh/GB × 494] × (new share + returning share × (1 − cached share))
Model v4 energy intensities per GB: data centres 0.055 operational + 0.012 embodied, networks 0.059 + 0.013, user devices 0.080 + 0.081 — 0.3 kWh/GB in all. The grid intensity defaults to the world average of 494 g CO2e/kWh. Green hosting sets the data centre's operational emissions to zero.
Example
A 2 MB page is 0.002 GB. 0.002 × 0.3 kWh/GB = 0.0006 kWh per view, and × 494 g/kWh = 0.2964 g CO2e, which is in the E band (0.279–0.359 g). At 10,000 views a month that is 120,000 views a year: 35.6 kg CO2e and 72 kWh. Verified green hosting brings it to 0.242 g (band D).
Frequently asked questions
Why not just enter my URL?
This site has no server that downloads other websites, and browsers block pages from reading other sites. Your browser's developer tools give the exact transfer size, including images and scripts loaded later.
What makes the biggest difference?
Page weight. Halving the transfer halves the estimate, and images, video and third-party scripts are usually the largest part. Caching helps returning visitors; green hosting removes about 18% of the total in this model.
Is this an exact footprint?
No. It is a model based on global averages of energy per gigabyte. It is good for comparing pages and tracking improvements, not for carbon accounting of a specific data centre.
Sources
Last updated:
Page address with these inputs: https://kakao.mobile/tools/website-carbon-calculator/
Cite or embed this tool
kakaoCalc. (2026, November 8). Website Carbon Calculator (from Page Weight). https://kakao.mobile/tools/website-carbon-calculator/
“Website Carbon Calculator (from Page Weight).” kakaoCalc, 8 Nov. 2026, kakao.mobile/tools/website-carbon-calculator/.
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