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What does a slow page load cost your website?

17 October 2026

Our earlier posts worked out how much traffic it takes to earn $100 and $1,000 a month, how long that traffic takes, what a returning visitor is worth and what a bounce costs. This one looks at the cause behind many of those bounces: what does a slow page cost?

How a slow page costs you money

A slow page loses people before they read. Some leave before the page appears, some read one page instead of three, and fewer of them buy or sign up. The research puts numbers on it:

• Conversion rates drop an average of 4.42% for each extra second of load time between 0 and 5 seconds (Portent, 2019, across 100 million page views).
• The chance of a bounce rises 32% as mobile load goes from 1 to 3 seconds, and 90% from 1 to 5 seconds (Think with Google, 2017).
• A mobile site 0.1 seconds faster saw 8.4% more retail conversions (Deloitte for Google, "Milliseconds Make Millions", 2020).

The calculator uses Portent's figure, compounded: each second faster multiplies earnings by 1 / (1 - 4.42%), and each second slower by (1 - 4.42%).

Earnings at a new load time = earnings now x 0.9558 ^ (seconds now - new seconds)

Work out your own cost

Type your visits a month, pages per visit, RPM, any other earnings, your load time now and a target. The calculator shows your earnings now, what the target would earn, what each second faster or slower is worth, and a 12-month earnings chart at three load times - in dollars and rand.

Prefer a full page? Open the cost of slow page load calculator on CalcSA. From there, the cost of bounce rate calculator shows what the visitors who do arrive and leave after one page cost.

Worked example: a 5,000-visit site

5,000 visits a month, 2.5 pages a visit, a $5 RPM, loading in 4 seconds, aiming for 2.

• Now: 5,000 x 2.5 = 12,500 page views x $5 / 1,000 = $62.50 a month, $750 a year.
• At 2 seconds: $62.50 / 0.9558 / 0.9558 = $68.41 a month - 9.5% more.
• Flat traffic: $5.91 a month, about $71 a year more.
• Traffic growing 3% a month: the year brings about 70,960 visits and $887 at 4 seconds, so the same 2 seconds are worth about $84.
• One second faster (4 to 3) = $2.89 a month. One second slower (4 to 5) costs $2.76 a month.

Ads are the small end of this. A site that also earns $500 a month from sales or leads, at the same 4.42% a second, would gain about $47 a month from the same 2 seconds - put it in the "Other earnings" box.

Estimates. 4 seconds now, a 2-second target, 2.5 pages a visit and 3% growth a month are our assumptions, as in the calculator. Portent measured conversions, not ad page views - applying 4.42% to ad earnings is our estimate, and beyond 5 seconds it is an extrapolation. The $5 RPM is the midpoint of the travel, food and home tier in Aditude's RPM for Publishers (July 2025) - not your rate.

Every second counts, the first ones most

Same site, same 5,000 visits a month, six load times:

• Each second is worth roughly $3 a month here - slightly more for each second you take off than for each you add, because the loss compounds.
• Going from 6 seconds to 2 is worth about $11 a month - the same as finding about 990 more visitors at 6 seconds.
• The real gain is bigger than the ad line. A faster page also keeps the visitors who would have left before the counter even counted them.
• Google's own benchmark is 2.5 seconds or less for Largest Contentful Paint - above 4 seconds it rates a page poor.

Reading your counter for this

A counter counts the visits that loaded. The ones who gave up waiting never reach it - so what WebCounter shows is what you earn at your load time now, and the calculator scales from there.

• Visits a month = your last 30 days of visits on your free WebCounter report.
• Pages per visit = page views / visits on the same report. 12,500 page views from 5,000 visits is 2.5.
• Watch returning visitors after you speed up. A site that is quick to come back to gets come back to - a rising share of returning visitors is one of the first signs the change is working.
• Watch the pages list for heavy pages - big images, embeds and many scripts - with many views but low pages per visit. Those are the ones to fix first.
• Compare before and after with the same counter. Note the date you made the site faster and compare pages per visit over the 30 days either side; WebCounter filters bots out, so the change you see is real readers.
• Measure your load time with Google's free PageSpeed Insights - use the Largest Contentful Paint figure as "load time" in the calculator.

Sources

• Portent, "Site Speed is (Still) Impacting Your Conversion Rate" (2019) - conversion rate falls an average of 4.42% for each extra second, 0 to 5 seconds. Not re-checked at the original on 17 October 2026; figure as cited in the CalcSA calculator.
• Think with Google, "Find out how you stack up to new industry benchmarks for mobile page speed" (2017) - bounce probability +32% from 1 to 3 seconds, +90% from 1 to 5. Not re-checked at the original on 17 October 2026.
• Deloitte for Google, "Milliseconds Make Millions" (2020), published on Think with Google - 8.4% more retail conversions from a 0.1-second faster mobile site. Not re-checked at the original on 17 October 2026.
• web.dev, "Largest Contentful Paint (LCP)" - 2.5 seconds or less is good, above 4 seconds is poor. Not re-checked at the original on 17 October 2026.
• Aditude, RPM for Publishers (23 July 2025) - $5 is the midpoint of the travel, food and home tier.
• Calculator: CalcSA, Cost of slow page load - rand amounts at the European Central Bank reference rate.

Estimates only. How much speed is worth depends on your audience, device mix, niche and ad setup; your own counter and ad dashboard beat any average.