Website Carbon Calculator

Estimate how much CO₂ one page view causes, and how to cut it.

Private by design

Your inputs stay on your device and are not sent to our servers. Optional usage analytics does not receive your files or tool inputs.

Website Carbon Calculator

CO₂ per page view · Sustainable Web Design Model v4

Page weight

Total transferred size from the browser Network tab.

Page views per month

Hosting

Visitors

New visitors

The rest are returning visitors.

Cached share for returning visitors

Advanced

Grid intensity

g/kWh

World average used by the model. Leave unchanged unless you have a better figure.

CO₂ per page view0.324 g0.00066 kWh

Per 1,000 views324 g

Per month6.49 kg

Per year78 kg

Where the CO₂ comes from (g per view)

Ways to cut it (each on its own) (4 rows)

Change	Per year	Saved	Saved %
Cut page weight by 25%	58 kg	19 kg	25%
Cut page weight by 50%	39 kg	39 kg	50%
Cache more for returning visitors (80% cached)	63 kg	15 kg	20%
Move to a verified green host	64 kg	14 kg	18%

How it works

Every byte a page sends uses electricity in data centres, networks and the visitor's phone or laptop, plus the energy used to build that equipment. The Sustainable Web Design model turns data transferred into an average CO₂ estimate.

Most of it happens on the visitor's device
Hosting choices change a smaller part. Page weight and caching reduce every part.

Data transferred = 2.2 MB = 0.0022 GB.
Visit factor = new + returning × (1 − cached) = 0.995.
Energy = 0.300 kWh/GB (with the green-host reduction applied) × GB × visit factor = 0.000657 kWh.
CO₂ = energy × 494 g/kWh = 0.324 g per page view.

Compress and resize images, and use modern formats such as WebP or AVIF.
Load scripts and video only when needed, and set long cache times for files that rarely change.
Ask your host whether it is verified green (the Green Web Foundation keeps a public check).

Sustainable Web Design Model v4 (sustainablewebdesign.org/estimating-digital-emissions). Energy per GB: data centres 0.055 operational + 0.012 embodied; networks 0.059 + 0.013; devices 0.080 + 0.081 kWh. Emissions = energy × grid intensity (494 g CO₂e/kWh world average, Ember), × [new + returning × (1 − cached)]. Green hosting reduces only the data-centre operational term. The new/returning and cache defaults are common assumptions, not part of the model; change them to match your site.

Preparing tool

How to use Website Carbon Calculator

Enter your page weight in MB (from the browser Network tab) and monthly page views.
Set hosting, new visitors and caching, or keep the defaults.
Read the grams per view and the yearly total, then compare the ways to cut it.

Read the detailed guide →

What are the limits of Website Carbon Calculator?

An estimate from a published average model, not a measurement of your own servers. You enter the page weight; nothing is fetched from any site. Your data stays on your device.