PageSpeed.ONE Score (SPS): How Do We Calculate User Web Speed?
The realm of web speed and its measurement can be quite daunting for the uninitiated. Consider the metrics alone. To truly grasp the state of your website as experienced by users, you need to monitor at least six numerical values from Core Web Vitals for each domain or subdomain.
That's why we've introduced a single number that acts as a proxy metric for Core Web Vitals on both mobile and desktop. We call it the “PageSpeed.ONE Score” (SPS).
In this text, you'll learn about the motivation behind SPS, how we calculate this speed score, and what's new in its 2025 version.
Why Seek a Single Number to Represent Overall Web Speed?
To genuinely understand the speed of your website for your users, you need to know the following:
- The differences between various measurement types (CrUX, synth, RUM).
- Details about Google's user data collection methods, specifically the Chrome UX Report.
- The values of all three Core Web Vitals metrics – LCP, CLS, INP – for all your websites, separately for mobile and desktop.
It's no surprise that people tend to simplify speed into something like the Lighthouse score (LPS), which claims to be the "one number for the entire web." However, using it to measure web speed is utterly misguided. Completely misguided.
This is precisely the issue our PageSpeed.ONE Score (SPS) addresses. It offers a single number that better reflects the actual web speed as experienced by users.
Calculation of PageSpeed.ONE Score
Below you'll find the updated process for calculating SPS, reflecting how real users perceive speed:
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From the Chrome UX Report, we take the current values of the three Core Web Vitals metrics for the entire domain or URL, separately for mobile and desktop.
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We consider user distribution, not just the 75th percentile. Even if the 75th percentile is "green," a significant portion of the audience may experience a slower web.
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Each metric carries different weights. LCP holds the highest weight due to its frequent correlation with conversions. CLS and INP have lower weights.
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We consider both mobile and desktop data, with their respective share in the calculation determined by the actual traffic distribution for the given site. There is no fixed mobile vs. desktop ratio.
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The score is calculated as a percentage. The best theoretical value is 100%, but it's practically unattainable.
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The score has three value zones: 0–25 red; 25–75 yellow; 75–100 green.
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If any of the Core Web Vitals metrics falls into the orange zone, the resulting SPS will also be limited to the orange zone.
The result is a single number on a 0–100% scale that indicates the web speed condition for real users and better spreads across the entire scale than before.
In the Summary Report, you will see the SPS for mobile and desktop, as well as for individual device types separately.
What's New in the 2025 Version?
The new SPS version, launching on November 28, 2025, brings several key changes:
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Stricter on Fast Websites A score above 95% is exceptional, and 100% is nearly unreachable.
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End of Clusters at Values 89 and 99 Finer calculations within all zones. Sites naturally spread across the entire scale, which is important for rankings and Awards.
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Incorporating User Distribution Not just the 75th percentile. SPS now also shows how large a portion of users truly meet the Core Web Vitals.
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Mobile vs. Desktop Based on Real Traffic Device weights are not fixed. Each site is set according to where its users are actually coming from.
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SPS History and Distribution In the Domains and Pages reports, you can now see the historical development of SPS and user distribution across different speed categories. This greatly simplifies understanding how your site's speed changes over time.
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Ready for Rankings The new calculation is designed to fairly rank e-commerce sites and large websites within the PageSpeed.ONE Awards and other studies.
We believe that the PageSpeed.ONE score will simplify navigating the speed of your websites. Nonetheless, it's crucial to understand how to handle this new metric.
How to Read the PageSpeed.ONE Score?
The PageSpeed.ONE web speed score is a "proxy metric." It can assist those who do not delve into web speed as intensively as developers do.
The target audience for the SPS metric includes website owners, marketers, project managers, and so on. The score shows the current state, but also, over time, the historical speed development of a specific domain for users, all encapsulated in a single percentage value.
However, our score is by no means intended to replace monitoring speed at the level of Core Web Vitals and thus the three metrics for two types of devices.
PageSpeed.ONE Score is Not a Replacement for Core Web Vitals
Core Web Vitals metrics provide more insight into the state of three speed areas:
If you embark on optimizations, focusing on these specific metrics should be your first step. It's also important to note that the SPS metric won't show how Google evaluates the speed of your domains or pages.
For optimization needs and setting goals, we recommend tracking both the SPS value and the Core Web Vitals metrics.
Where Can You Obtain the PageSpeed.ONE Score?
You can see the metric value in the Summary Report in PLUS monitoring, and it's also available for free measurement on our website – pagespeed.cz.