Amazon calculated that every 100 milliseconds of load time costs them 1% in sales. That's roughly $38 million per 100ms, per year.
Google found that a 0.5 second delay in search results reduced traffic by 20%.
Walmart discovered that for every 1 second improvement in load time, conversions increased by 2%.
These aren't small companies with small margins. These are the most sophisticated data operations in the world, and they're obsessing over milliseconds.
Why? Because speed is money. And the math applies to your website too.
The Speed-Conversion Curve
Here's what the data consistently shows across our client sites and industry research:
- 0-2 seconds: Optimal. This is where you want to be. Users perceive the site as "fast" and engage normally.
- 2-3 seconds: Acceptable. Some users notice the delay, slight drop in engagement.
- 3-5 seconds: Problematic. 40% of users will abandon. Mobile users are especially impatient.
- 5+ seconds: Critical. You're losing the majority of visitors before they even see your content.
The relationship isn't linear—it's exponential. Going from 5 seconds to 3 seconds has a bigger impact than going from 3 seconds to 1 second.
The Real Cost: A Calculator
Let's make this concrete with actual numbers.
Assumptions:
- 1,000 monthly visitors
- 5% conversion rate (at optimal speed)
- $100 average order value
- Current load time: 6 seconds
At 6 seconds load time:
- 53% of visitors bounce before page loads (industry data)
- Effective visitors: 470
- Conversions: 23.5 (470 × 5%)
- Revenue: $2,350/month
At 2 seconds load time:
- 9% bounce before page loads
- Effective visitors: 910
- Conversions: 45.5 (910 × 5%)
- Revenue: $4,550/month
The difference: $2,200/month, or $26,400/year.
And this is conservative—a slow site doesn't just lose visitors, it also converts worse among those who stay. The psychology of a slow site bleeds into trust: "If their website is this slow, how will their product/service be?"
What Actually Slows Down Websites
When we audit slow sites, we find the same culprits over and over. Here's where the time goes:
1. Images (40-60% of load time)
The biggest offender, by far. Common problems:
- Uncompressed images: A 5MB hero image that should be 200KB
- Wrong format: JPEG/PNG when WebP would be 50% smaller
- Oversized dimensions: A 4000px wide image displayed at 800px
- No lazy loading: Loading all 20 images immediately instead of as user scrolls
We've seen single image optimizations cut load time in half.
2. JavaScript (20-30% of load time)
Every script you add costs performance:
- Analytics overload: Google Analytics + Facebook Pixel + Hotjar + 5 other trackers = 500KB+ of JavaScript
- Unused libraries: Loading jQuery when you use 2 functions from it
- Render-blocking scripts: JavaScript that prevents the page from displaying until it loads
- Chat widgets: That "helpful" chat bubble often adds 200ms+ to load time
3. Fonts (10-15% of load time)
- Too many weights: Loading 6 font weights when you use 2
- Full character sets: Loading Cyrillic and Greek when your site is English-only
- Flash of unstyled text (FOUT): Font loading that makes text flicker
4. Server/Hosting (10-20% of load time)
- Slow hosting: Cheap shared hosting with slow response times
- No CDN: Serving files from one server location instead of edge nodes
- No caching: Regenerating pages that could be served from cache
The Fixes That Actually Matter
Here's exactly what we do on every site to ensure sub-2-second load times:
Image Optimization (Priority 1)
Step 1: Convert to WebP
WebP is 25-35% smaller than JPEG at equivalent quality. Modern browsers all support it. There's no reason not to use it.
Step 2: Right-size images
If an image displays at 800px wide, the file should be 800px wide (or 1600px for retina). Not 4000px.
Step 3: Compress aggressively
For photos, 80% quality is visually identical to 100% but often 60% smaller. Use tools like Squoosh or TinyPNG.
Step 4: Lazy load below-fold images
Images the user can't see yet shouldn't load until they scroll. Native lazy loading (loading="lazy") works in all modern browsers.
Step 5: Use responsive images
Serve smaller images to mobile devices. A phone doesn't need the same resolution as a desktop monitor.
JavaScript Optimization (Priority 2)
Step 1: Audit every script
List every JavaScript file loading. For each one, ask: "Is this essential? Can it load later?"
Step 2: Defer non-critical scripts
Analytics, chat widgets, and tracking pixels can load after the page is interactive. Use defer or async attributes.
Step 3: Remove unused scripts
That carousel library you used once on a page that no longer exists? Delete it. That social sharing widget no one uses? Gone.
Step 4: Consider the real cost of each tool
Every chat widget, popup, and tracker has a speed cost. The question isn't "does this help?" but "does this help more than the conversions lost to slower speed?"
Font Optimization (Priority 3)
Step 1: Subset fonts
If you only use Latin characters, don't load Greek, Cyrillic, and Vietnamese character sets.
Step 2: Limit weights
Regular and Bold cover 90% of use cases. Every additional weight is another file to download.
Step 3: Preload critical fonts
Tell the browser to start downloading fonts immediately, not after it discovers them in CSS.
Step 4: Use font-display: swap
Show text immediately in a fallback font while custom fonts load. Prevents blank text flashing.
Hosting and Delivery (Priority 4)
Step 1: Use a CDN
A CDN (Content Delivery Network) serves files from servers near your users. Someone in Tokyo shouldn't wait for files from New York.
Step 2: Enable caching
Static assets (images, CSS, JS) should be cached in browsers. Users who visit twice shouldn't re-download everything.
Step 3: Choose fast hosting
Vercel, Netlify—these platforms are optimized for speed. A $5/month shared host is not.
Measuring Speed: The Metrics That Matter
Google's Core Web Vitals are the standard for measuring speed. Here's what they mean:
Largest Contentful Paint (LCP)
How long until the main content is visible. Target: under 2.5 seconds.
First Input Delay (FID) / Interaction to Next Paint (INP)
How long until the page responds to user interaction. Target: under 100ms.
Cumulative Layout Shift (CLS)
How much the page "jumps" as it loads. Target: under 0.1.
Tools to measure:
- Google PageSpeed Insights (free, uses real user data)
- GTmetrix (detailed waterfall analysis)
- WebPageTest (advanced testing from multiple locations)
- Chrome DevTools (real-time performance tab)
Real Client Example
A creator came to us with a course sales page that was converting at 1.2%.
Initial audit:
- Load time: 8.2 seconds
- Hero image: 4.7MB PNG
- 13 JavaScript files loading synchronously
- 7 font files
- No caching headers
What we fixed:
- Compressed and converted hero to 180KB WebP
- Removed 8 unused scripts, deferred remaining 5
- Reduced to 2 font files with subsetting
- Added proper caching
- Migrated to faster hosting with CDN
Results:
- New load time: 1.8 seconds
- Bounce rate: down 42%
- Conversion rate: up to 3.1%
- Revenue increase: $47,000/year (on same traffic)
The optimization took 4 hours. The ROI is essentially infinite.
The Speed Checklist
Run through this on any site:
Images
- ☐ All images in WebP format
- ☐ All images properly sized (not larger than display size)
- ☐ All images compressed (80% quality or less for photos)
- ☐ Below-fold images lazy loaded
- ☐ Responsive images for mobile
JavaScript
- ☐ No unused scripts
- ☐ Non-critical scripts deferred
- ☐ Third-party scripts evaluated for necessity
- ☐ No render-blocking JavaScript
Fonts
- ☐ Maximum 2 font families
- ☐ Fonts subsetted to needed characters
- ☐ Critical fonts preloaded
- ☐ font-display: swap enabled
Hosting
- ☐ CDN enabled
- ☐ Proper cache headers set
- ☐ HTTPS enabled
- ☐ HTTP/2 or HTTP/3 supported
The Bottom Line
Website speed isn't a technical concern—it's a business concern.
Every second of load time costs you money. Not in some abstract, hard-to-measure way, but in real, trackable revenue.
The good news: speed optimization is one of the highest-ROI activities you can do. A few hours of work can generate thousands of dollars in additional annual revenue.
The math is simple. Fast sites make more money. Slow sites lose visitors before they even see your offer.
Measure your speed. Fix the obvious issues. Watch your conversions improve.
Milliseconds matter.
