What's your slow site costing you?
Your traffic, your average sale, your load time. Every assumption sits in the open and you can adjust all of them, so the number you get is yours, not a marketing stat.
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Don't know it? Measure it with Google's PageSpeed Insights, right here:
This is the one assumption in the math. Published research (Google's mobile bounce benchmarks, the Akamai/SOASTA retail study, Google and Deloitte's "Milliseconds Make Millions") supports a per-second cost roughly in this range depending on audience and device mix. Drag it wherever you find credible and watch the number move.
Estimated revenue lost to load time
$0/mo
$0 a year, at your own numbers
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How the math works
It follows your traffic to sales, then takes out the share it estimates a slow load costs.
lost a month = visitors × lead rate × close rate × average sale × share lost
share lost = 1 - (1 - loss per second)seconds past 2
- Visitors 1,000, lead rate 3%, sale $500, load 5 seconds. Examples, not benchmarks. Put in your own.
- Close rate 30%. A lead is a call or a form, not a sale, so only leads who become customers count.
- The 2-second line. At or under it, nothing counts as lost. Google's web.dev calls a Largest Contentful Paint of 2.5 seconds or less good, so my line is a bit stricter.
- 5% per extra second. Each second past 2 costs 5% of the leads still left, so 3 extra seconds cost 14%, not 15%. It's my assumption; the slider changes it.
- Today's lead rate. If you type in what the slow site gets now, that rate has already shrunk, so the real loss runs higher than shown. I kept the math low on purpose.
- The payback line. $4,500, my full build's starting price, divided by your monthly loss. Arithmetic, not a promise that a new site wins it all back.
Source: web.dev, "Largest Contentful Paint (LCP)," checked Sep 2026.
Where the 5% comes from
Three studies point the same way, though none measured your business:
- Google/SOASTA, 2017. As mobile load time goes from 1 to 3 seconds, the chance of a bounce rises 32%. From 1 to 5 seconds, 90%. From 1 to 10, 123%.
- Google and Deloitte, "Milliseconds Make Millions," 2020. On 37 brand sites, a mobile site 0.1 seconds faster saw retail conversions rise 8.4%.
- Portent's rolling research, updated 2022. Ecommerce pages averaged a 3.05% conversion rate at 1 second and 0.67% at 4 seconds.
Both conversion studies found bigger effects than 5% a second. But Deloitte studied big brands, and Portent compared different pages, so part of its gap is probably the pages. I start at 5%, and the slider goes from 2% to 10%.
Sources: Think with Google (2017), Deloitte and web.dev (2020), Portent (2022), all checked Sep 2026.
A worked example
A cleaning company's site gets 1,500 visits a month and loads in 4 seconds on a phone. 4% of visitors call or send the form, 1 in 4 of those leads books, and a typical job is $400.
- Leads: 1,500 × 4% = 60 a month.
- Customers: 60 × 25% = 15, worth 15 × $400 = $6,000.
- Seconds past the line: 4 - 2 = 2. Share lost: 1 - 0.95 × 0.95 = 9.75%.
- $6,000 × 9.75% = $585 a month, $7,020 a year. That adds up to the $4,500 build price about every 8 months.
Slide the assumption to 2% and it's $238 a month. At 10%, it's $1,140. Load this example into the calculator.
How to read your number
Speed isn't your leak
Your site loads in 2 seconds or less. Check clarity, trust, follow-up, and findability instead, with the free Website Leak Scanner.
Real, but small
The leak needs over 3 years to reach $4,500. Don't rebuild for speed alone. Fix what's cheap on the site you have.
Worth fixing this year
Do the free fixes first: image sizes, extra scripts, fonts. Measure again. If the theme or host is still the weight, price a rebuild.
Worth fixing now
The leak passes a build's price inside a year. Confirm your load time on PageSpeed Insights, then fix it this month. If the theme or host is the cause, that's when I'd talk about a rebuild.
Find your real load time
Your own phone on your wifi can flatter the site. Google's free PageSpeed Insights gets closer to a customer's view. The Measure my site button above runs it for you through Google's PageSpeed Insights API. To run it yourself:
- Go to pagespeed.web.dev, paste your home page address, and press Analyze.
- Stay on the Mobile tab.
- Under "Discover what your real users are experiencing," read Largest Contentful Paint: when the main content shows, for real Chrome users over 28 days. 3 in 4 page loads were that fast or faster. That's your number.
- If it says No Data, your site has too few visits in Google's data. Use Largest Contentful Paint under "Diagnose performance issues": a lab test on an emulated Moto G Power over slow 4G. Lab values vary, so run it twice.
More on testing like a customer: how fast should a website load.
Source: Google PageSpeed Insights and its documentation, checked Sep 2026.
What a fast site takes
Small-business sites are usually slow for ordinary reasons that stack up: oversized photos, a heavy page-builder theme, too many scripts and fonts, crowded hosting. Why is my website slow ranks them, and the first few are often fixable on the site you have.
When the builder or theme is the weight, tuning hits a ceiling. That's what my full build is for: hand-coded, static-first pages with almost no JavaScript, on free Cloudflare hosting, from $4,500. The process page shows this site's own dated PageSpeed scores.
Questions people ask
How much is a slow website costing me? +
About $642 a month at this calculator's example numbers: 1,000 visitors, a 3% lead rate, 30% of leads buying, a $500 sale, and a 5-second phone load. Yours will differ.
Does page speed really affect sales? +
Yes, in all three studies on this page, though none measured your business. Google/SOASTA (2017) found the chance of a mobile bounce rises 32% as load time goes from 1 to 3 seconds, and Google and Deloitte (2020) saw retail conversions rise 8.4% on mobile sites 0.1 seconds faster.
How do I check my website's load time? +
Press Measure my site on this page: it runs Google's PageSpeed Insights on a phone and fills in Largest Contentful Paint, the real-user number if Google has one, otherwise the lab number. Or run it yourself at pagespeed.web.dev and read Largest Contentful Paint on the Mobile tab.
Will a new website fix a slow load time? +
Only when the platform or theme is the weight. Oversized images, extra scripts, and heavy fonts are usually fixable on the site you have, so start there and measure again.
Not loving that number?
Speed is the most fixable leak there is: my builds ship static-first and publish dated speed receipts. Limited builds per month, free call, real plan either way.