EcoIndex is a score out of 100. The higher the score, the better the environmental performance.
This representation is the most commonly used on the web to evaluate other dimensions such as quality, performance, accessibility, etc.
The boundaries of the EcoIndex scale (0 to 100) were developed and validated by analyzing the HTTParchive database (500,000 URLs).
The EcoIndex is calculated from three objective physical measures: DOM size, KB transferred, number of HTTP requests. These three indicators are associated via a weighted average with 3 for the DOM, 2 for the HTTP requests and 1 for the weight of the transferred data.
Calculation formula :
In order to take into account the disparity in the measurements of the 3 indicators (DOM, KB, HTTP requests), we position the observed value (DOM, HTTP requests, KB) in a quantile taking into account its proximity to the lower/upper bounds of the quantile.
Once the EcoIndex is obtained, we rank this value against the other values in the EcoIndex database. We thus obtain a rank. We distribute the ranks on a scale from A to G (European standard). So you get a second information: the performance of the URL compared to the other tested URLs.
It is therefore a performance relative to the sample studied.
Finally, the environmental footprint is calculated according to the level of eco-design of the site.
We start with an average impact (2g CO₂eq) in terms of greenhouse gas emissions and fresh water consumption.