Milliseconds Make Millions: What Google's Own Research Shows About Website Speed and the Cost of a Slow Page

Abstract

Google's own commissioned research puts an exact number on something most small business owners only feel anecdotally: a slow website costs real money. In a study of 37 brand sites and more than 30 million user sessions, Google, fifty-five, and Deloitte found that a mobile speed improvement of just one-tenth of a second (100 milliseconds, less time than it takes to blink) was associated with an 8.4% increase in retail conversions and a 10.1% increase in travel conversions. Meanwhile only about a third to just under half of websites currently pass Google's own Core Web Vitals thresholds, meaning most sites, including many built for small businesses, are leaving this specific, well-documented lever untouched. This study explains what Core Web Vitals measure, what the landmark Milliseconds Make Millions study found, and why more than half of mobile visitors walk away from slow pages before a business gets the chance to make its case.

Methodology

This report is based primarily on Milliseconds Make Millions, a study commissioned by Google and conducted by fifty-five and Deloitte Digital in late 2019, analyzing mobile site data from 37 brand websites across retail, travel, luxury, and lead-generation sectors in Europe and the United States, tracking speed and business outcomes hourly over a 30-day period totaling more than 30 million user sessions. It also draws on Google's official Core Web Vitals documentation and threshold-setting research (Google Search Central and web.dev), Google's published web.dev case studies (Vodafone Italy, Rakuten 24, and RedBus), Google's The Need for Mobile Speed research (Google and SOASTA), and current HTTP Archive and Chrome User Experience Report (CrUX) data on Core Web Vitals pass rates. Some secondary sources report slightly different exact percentages for select Milliseconds Make Millions findings, particularly for luxury and lead-generation sectors, reflecting variation across different published summaries of the same underlying report; this report notes that variation explicitly rather than presenting a false precision. Website speed's business impact varies by industry, starting performance, and specific implementation, and this report does not constitute a guarantee of results for any individual business or website.

Findings

Google's Core Web Vitals define specific thresholds for a good page: Largest Contentful Paint (LCP) under 2.5 seconds, Interaction to Next Paint (INP) under 200 milliseconds, and Cumulative Layout Shift (CLS) under 0.1, all measured at the 75th percentile of real visits. Core Web Vitals have been a confirmed ranking factor since the 2021 Page Experience Update, functioning as a tiebreaker between otherwise similar pages. Yet most sites do not meet the bar: only about 48% of mobile origins and 56% of desktop origins pass all three thresholds as of 2025 tracked data, with some compilations placing the all-three figure closer to a third overall, and LCP the hardest to pass at roughly 58 to 62% of mobile pages. The Milliseconds Make Millions study of 37 brand sites and more than 30 million sessions found that a natural 0.1-second mobile speed improvement was associated with an 8.4% rise in retail conversions, a 9.2% rise in retail average order value, a 10.1% rise in travel conversions, and up to a 21.6% rise in lead-generation form submissions. Google web.dev case studies confirm the pattern: Vodafone Italy saw 8% more sales from a 31% better LCP, Rakuten 24 saw a 53.37% increase in revenue per visitor from a good LCP, and RedBus saw a 7% sales increase from improved INP. Separately, Google found 53% of mobile visitors abandon a page that takes longer than 3 seconds to load.

Overview

Website speed is one of the most measured, best-documented factors in digital marketing, and yet it remains one of the most commonly overlooked when a small business decides where to invest. Behind SEO, ads, and content, speed rarely gets its own line item. Google’s own research suggests that is a mistake. This report walks through what Google’s Core Web Vitals program actually measures and why it exists, what the landmark Milliseconds Make Millions study (commissioned by Google, conducted by fifty-five and Deloitte) found when it tracked 30 million real user sessions across 37 brand websites, what Google’s own published case studies show happened when specific companies improved their site speed, and why more than half of mobile visitors are walking away from slow pages before a business ever gets the chance to make its case. The throughline is consistent: page speed is not a technical vanity metric. It is a measurable, revenue-moving lever that Google itself has spent years researching, documenting, and, as of 2021, building directly into how it ranks websites in search results.

Google’s standard for a good website has a specific number attached

Core Web Vitals are three specific metrics Google uses to measure real-world user experience, and Google’s own developer documentation defines clear thresholds for each. Largest Contentful Paint (LCP) measures how quickly the main visible content of a page finishes loading, with good defined as occurring within 2.5 seconds. Interaction to Next Paint (INP) measures how responsive a page feels when a visitor actually interacts with it, with good defined as under 200 milliseconds; INP replaced the earlier First Input Delay metric in March 2024. Cumulative Layout Shift (CLS) measures visual stability, whether elements on the page jump around as it loads, with good defined as a score under 0.1. Google’s own research team selected the LCP threshold specifically by combining human-perception research on how long a visitor waits before losing focus (roughly 1 to 3 seconds) with real-world achievability data from its own Chrome User Experience Report.

Google formally confirmed Core Web Vitals as a search ranking factor with its 2021 Page Experience Update, and continues to include them in its ranking systems today. Google’s own guidance describes their role accurately: not the single biggest ranking factor, but a real one, and specifically a tiebreaker between pages that are otherwise similar in content quality and relevance. In a competitive local search result, speed can be exactly what separates the business that ranks first from the one that does not.

Most websites do not actually meet Google’s own bar

Despite Core Web Vitals having been a confirmed ranking factor since 2021, most websites still do not meet the thresholds Google itself defines as good. Data from the HTTP Archive and Chrome UX Report, the same real-world dataset Google uses to evaluate Core Web Vitals, found only about 48% of mobile website origins and 56% of desktop origins meet all three thresholds simultaneously as of 2025 tracked data, with other compilations of the same underlying data placing the all-three-passing figure closer to a third of sites overall. LCP is consistently identified as the hardest metric to pass, with only around 58% to 62% of mobile pages currently achieving a good LCP score, depending on the specific dataset referenced.

This gap is precisely where the opportunity sits for a small business willing to invest in genuine site performance. Since the majority of competing websites in most markets are not meeting Google’s own bar, a site that does clear all three thresholds is not just following best practice, it is outperforming a meaningful share of the competition on a factor Google has confirmed it uses to help decide rankings.

A tenth of a second is enough to move real revenue

The most rigorous evidence connecting site speed directly to revenue comes from Milliseconds Make Millions, a study commissioned by Google and conducted by fifty-five and Deloitte in late 2019. Researchers analyzed mobile site data from 37 retail, travel, luxury, and lead-generation brands across Europe and the United States, tracking speed and business outcomes hourly over a 30-day period, totaling more than 30 million user sessions, one of the largest datasets ever assembled specifically to isolate the relationship between site speed and business results, with no other design or UX changes made to the sites during the study window.

The findings, based on a natural 0.1-second (100-millisecond) improvement in mobile site speed, were consistent across every sector studied: retail conversions rose 8.4%, with average order value up 9.2%; travel conversions rose 10.1%, with average order value up 1.9%; lead generation sites saw form submissions rise as much as 21.6% in some analyses; and luxury sites saw meaningful gains in page views per session and progression toward purchase. The study’s core conclusion, stated plainly in Google’s own summary, was that mobile site speed improvements had a direct, measurable correlation to improved progression through the entire purchase or conversion funnel, not just a single isolated metric.

Real companies, real results: what Google’s own case studies show

Beyond the aggregate research, Google has published specific, named case studies through its web.dev platform documenting individual companies that improved Core Web Vitals metrics and measured the direct business result. Vodafone Italy ran a controlled A/B test between two visually identical pages, with page performance as the only variable; the version with a 31% better LCP score generated 8% more sales, a 15% improvement in lead-to-visit rate, and an 11% improvement in cart-to-checkout completion. Rakuten 24 found that improving to a good LCP score produced a 53.37% increase in revenue per visitor and a 33.13% increase in overall conversion rate. RedBus improved its Interaction to Next Paint score specifically and saw a 7% increase in sales as a direct result.

These are not small, statistically noisy samples. They are controlled or closely monitored real-world tests from large, sophisticated companies with the analytics infrastructure to isolate speed as the specific variable driving the change. The consistency across Vodafone Italy, Rakuten 24, and RedBus, three different companies, three different markets, three different specific metrics improved, reinforces that the Milliseconds Make Millions findings are not a one-time statistical anomaly.

More than half of mobile visitors leave before your site even loads

Google’s own research has found that 53% of mobile website visitors will leave a page entirely if it does not load within 3 seconds, meaning a majority of prospective visitors on a slow-loading site never actually see the content, offer, or business behind it in the first place. This finding, from Google’s The Need for Mobile Speed research, was reinforced by a related comparison: mobile sites that loaded within 5 seconds saw 25% higher ad viewability, 70% longer average sessions, and a 35% lower bounce rate compared to sites that took 19 seconds to fully load.

For a local service business, this has a direct practical translation. Every marketing dollar spent driving a prospective customer to a slow website is a dollar with roughly a coin-flip’s chance of being wasted before the visitor ever reads a word of copy, sees a phone number, or considers filling out a contact form, independent of how good the ad, the offer, or the website’s actual design happens to be.

Practical implications

• Check where your own site actually stands against Google’s thresholds, since Core Web Vitals are measured using real visitor data (not a lab test), viewable directly through Google Search Console or PageSpeed Insights, the same data Google itself uses.
• Treat page speed as a marketing investment, not just a technical cleanup task, and evaluate a speed project with the same revenue-impact lens as an SEO or ad campaign, because the data suggests it can move the same numbers.
• Prioritize mobile performance specifically, since the majority of the research here (the Milliseconds Make Millions study, the 53% abandonment figure, and current Core Web Vitals pass rates) is about mobile, and mobile traffic makes up the majority of most local businesses’ website visits.
• Remember that speed is a ranking tiebreaker, not just a conversion lever, so a business competing for the same local search terms as several competitors may find site speed is precisely the factor deciding who ranks above whom.

These findings ground our Website Design and SEO work for North Atlanta small businesses, and they pair naturally with our companion study on the cost of a slow lead response. Explore the full research library for more.