# How do I calculate my website's carbon footprint?

Canonical: https://senseible.earth/answers/website-carbon-footprint-calculation

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](https://senseible.earth/calculators/cloud-data-centre-emissions)
- [SaaS subscriptions in Scope 3](https://senseible.earth/answers/saas-subscriptions-scope-3-emissions)
- [Grid electricity factor for India](https://senseible.earth/emission-factors/grid-electricity)

Sources: [ISO/IEC 21031:2024, Software Carbon Intensity (SCI) specification (iso.org)](https://www.iso.org), [CEA CO2 Baseline Database](https://cea.nic.in/cdm-co2-baseline-database/?lang=en), [GHG Protocol Corporate Value Chain (Scope 3) Standard](https://ghgprotocol.org/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.