What a 1-Second Faster Site Is Worth in Leads

“Faster is better” is easy to agree with and hard to budget for. When I quote speed work, the useful question isn’t whether it helps. It’s whether it helps enough to be worth the invoice. This post walks through how I answer that, with a worked example you can redo with your own numbers.

What the research actually supports

You’ll see one statistic quoted everywhere, usually something like “every second of delay costs 7% of conversions”. It gets repeated so often that its original source is hard to pin down. Here’s what better-documented studies say:

• Deloitte, commissioned by Google, studied 30 million mobile sessions across 37 brands. A 0.1-second improvement raised retail conversions by 8.4% and cut bounce rates on lead generation pages by 8.3% (Milliseconds Make Millions).
• Google’s own mobile research found the probability of a bounce rises by 32% as load time goes from one second to three (Think with Google).
• Portent analyzed around 100 million page views on B2B and B2C sites and found conversion rates were highest on pages that loaded in about a second, falling as load time rose (Portent).

None of these tell you what one second is worth on your site. Your audience, your offer and how slow you are today all change the answer. So instead of borrowing one number, I model a range.

Step 1: Write down your funnel

You need four numbers, all of which you probably already have in analytics or your CRM. Here’s a made-up but typical B2B service business:

• Monthly visitors: 3,000
• Visitor-to-lead conversion rate: 2% (60 leads a month)
• Lead-to-client close rate: 20% (12 new clients a month)
• Average deal value: $5,000

That gives a baseline of 12 × $5,000 = $60,000 a month in revenue that starts on the website.

Step 2: Model three scenarios

Now assume the site gets one second faster, and that it increases the conversion rate by a cautious 5%, a middling 10% or an optimistic 20%. These are relative lifts, so 2% becomes 2.1%, 2.2% or 2.4%. Everything else stays the same.

Even the cautious case is three extra leads and $36,000 a year. It looks small per month, but it compounds because the visitors were already arriving. You paid to get them there, through ads, SEO or referrals, and a slow page was letting some of them leave.

Step 3: Compare it with the cost

Divide the cost of the speed work by the monthly gain to get a payback period. If the work costs $4,000, the cautious scenario pays it back in about 1.3 months, and the middle scenario in under a month. If it costs $40,000, the cautious case takes more than a year to pay back (about 13 months), so I’d want good reason to believe the middle case, which pays back in under seven, before committing.

That’s the whole method. Its value isn’t precision. It turns a vague “speed matters” into a decision you can defend to whoever signs the cheque.

When the maths says don’t bother

• You’re already fast. Going from 1.5 seconds to 0.5 won’t move much. The big gains are slow sites getting reasonable. Going from five seconds to four matters far more.
• Traffic is tiny. A 10% lift on 200 visitors a month is a rounding error. Fix traffic first.
• The problem is the message. A fast page that doesn’t explain what you do still won’t convert. Speed amplifies a good page; it doesn’t rescue a bad one.

One extra benefit the model ignores: if you run Google Ads, landing page experience feeds into Quality Score, so a faster landing page can lower what you pay per click as well as converting more of those clicks.

Step 4: Run your own numbers

First, find out where you stand. Run your homepage and your main landing page through my free website analyzer or Google’s PageSpeed Insights, and check the Core Web Vitals report in Search Console for what real visitors experience.

Then measure. After the speed work ships, compare conversion rate for the four weeks before and after, on the same pages, and ideally the same traffic sources. That’s your real number, and next time you won’t need to borrow anyone else’s.

Frequently Asked Questions

How much does a faster website increase conversions?
It depends on the site. Deloitte found a 0.1-second mobile improvement lifted retail conversions 8.4% and cut lead-gen bounce rates 8.3%. Plan with a range, and measure after launch.

How do I calculate what site speed is worth?
Visitors × conversion rate × close rate × deal value, before and after a modeled lift. Compare the difference with the cost of the work.

Does speed matter if my site already loads in under two seconds?
Much less. The biggest gains come when slow sites become reasonable.