How do I calculate my website's carbon footprint?

Multiply the data transferred per page view by monthly page views, then by an energy intensity per GB from a published model such as the Sustainable Web Design Model, then by a grid factor. The result is a model-based estimate, and different methods give quite different numbers, so state the method.

The inputs you need

• Page weight: kB or MB transferred per view, from your browser's developer tools or a page test, averaged over your main pages.
• Page views per month, from your analytics.
• Energy per GB: the figure the model you use publishes, covering data centres, networks and user devices.
• Grid factor: where most of the energy is used. For an Indian audience and hosting, 0.710 kg CO2 per kWh (CEA, version 21.0).

Where the result sits in your inventory

Hosting you pay for is Scope 3 Category 1; servers on your own electricity bill are Scope 2. Energy used by visitors' phones and laptops is not your Scope 1 or 2 and is not a purchase, so most inventories leave it out; website models include it because it is part of the system your pages drive. Report a website estimate as a separate metric, not as an added line in your Scope 1, 2 and 3 totals.

Why tools disagree

• They use different energy per GB figures and different splits between data centre, network and device.
• Some count returning visitors' cached pages as smaller transfers, others do not.
• Some apply a global average grid factor, others the visitor's country.
• Fix one method, record its version, and track the trend rather than comparing with another tool's number.

What actually cuts it

• Compress and resize images, and serve modern formats.
• Remove unused scripts, fonts and trackers.
• Cache static files so repeat visits transfer less.
• Host in a region with lower grid intensity if latency allows.

Worked example: a D2C store

• Page weight 2 MB x 100,000 views a month = 200,000 MB = 200 GB
• 200 GB x 0.2 kWh per GB (illustrative intensity) = 40 kWh
• 40 x 0.710 kg CO2 per kWh = 28.4 kg CO2 a month, about 341 kg a year

The 0.2 kWh per GB is a placeholder. Use the energy intensity published in the current version of the model you choose.

What Senseible does here

Senseible reads your hosting and SaaS invoices into its Scope 3 evidence trail, and its cloud and data centre calculator estimates hosting emissions from usage by region.

• Cloud and data centre emissions calculator
• SaaS subscriptions in Scope 3
• Grid electricity factor for India

Sources: ISO/IEC 21031:2024, Software Carbon Intensity (SCI) specification (iso.org), CEA CO2 Baseline Database, GHG Protocol Corporate Value Chain (Scope 3) Standard

Last reviewed 2026-10-18. Website models such as the Sustainable Web Design Model are revised; record the version and recheck its energy intensity figures when it changes.