From Site Speed to Revenue: A Loadtime Impact Calculator for Founders
July 31, 2026
2 min read
by Max Tymoshyn
Every e-commerce founder has been told site speed matters. Almost none have a number attached to it. “Make the site faster” sits on the backlog forever because it competes with launches and ads that come with a dollar sign. This is a loadtime impact calculator you can run on a napkin: it turns a vague performance problem into a revenue figure your team will actually prioritize.
The simple math
You need three inputs from analytics: monthly/annual sessions, conversion rate, and average order value. The base formula is Revenue = Sessions × Conversion rate × AOV. The speed layer adds one variable: how much conversion moves per second of load time. Portent, studying 100M+ page views, found conversion drops ~0.3 percentage points per added second, with the highest conversion in the 0–4 second band. So Adjusted revenue = Sessions × (Conversion ± speed effect) × AOV.
A worked example (illustrative)
200,000 sessions/yr, 3s baseline, 2.2% conversion, $85 AOV → baseline $374,000. Modeling ~9% relative conversion change per second:
| Page load time | Conversion impact vs 3s | Illustrative CR | Annual revenue | Effect vs baseline |
|---|---|---|---|---|
| 1 second | +18% | 2.60% | $441,320 | +$67,320 |
| 2 seconds | +9% | 2.40% | $407,660 | +$33,660 |
| 3 seconds (baseline) | 0% | 2.20% | $374,000 | $0 |
| 4 seconds | −9% | 2.00% | $340,340 | −$33,660 |
| 5 seconds | −18% | 1.80% | $306,680 | −$67,320 |
The spread between a 1-second and 5-second store is ~$134,000/yr on identical traffic. Nobody bought more; the page just showed up faster.
Why these effects are real
The Deloitte/Google study Milliseconds Make Millions tracked 30M+ mobile sessions across 37 brands and found a 0.1-second speed improvement lifted retail conversions 8.4% and AOV 9.2%. Vodafone Italy improved LCP 31% and saw 8% more sales. Different brands, same direction.
How to use it
- Get your real load time (PageSpeed Insights, field data).
- Pull sessions, conversion rate, AOV.
- Model one second faster with a conservative lift.
- Compare that gap against the cost of the fix.
Frequently Asked Questions
Want us to run this against your actual store data and pinpoint where you’re losing seconds — and revenue? Book a call with The Reach Bureau.
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