Portent: 1-second e-commerce sites convert 2.5x higher

Portent, a digital agency, went back to a question it has revisited across several years of its own data: does page load time actually move conversion rate, or is the relationship mostly folklore repeated from one blog post to the next. Its April 2022 analysis pulled from 20 of its sites and found conversion rate dropping steadily as load time rose, in both directions of its dataset.

What did the aggregate data show#

Portent split its sample into 6 B2C e-commerce sites and 14 B2B lead-generation sites, then compared conversion by load time. For e-commerce, conversion rate fell from 3.05% at a 1-second load to 1.68% at 2 seconds, 1.12% at 3 seconds, and 0.67% at 4 seconds. Portent’s text places the 0.67% at 4 seconds, so its 2.5x multiplier against 5 seconds cannot be reproduced from the published rates. Lead-generation sites moved from almost 40% at 1 second to 34% at 2 seconds and 29% at 3 seconds, and Portent reports a 3x gap against 5 seconds and a 5x gap against 10 seconds, which imply about 13% and 8%.

Load time	B2C conversion rate	B2B conversion rate
1 second	3.05%	~40%
2 seconds	1.68%	~34%
3 seconds	1.12%	~29%
4 seconds	0.67%	not reported
5 seconds	not reported	~13% (implied)
10 seconds	not reported	~8% (implied)

Portent’s own write-up is direct about the shape of the curve: “a site that loads in 1 second has a conversion rate 3x higher than a site that loads in 5 seconds” for B2B, and “2.5x higher than a site that loads in 5 seconds” for B2C e-commerce.

Why B2C and B2B sit so far apart#

The two conversion curves fall at similar rates proportionally, but their absolute levels are not close. Portent attributes that gap to what counts as a conversion in each case: “goal conversions on websites are generally achieved at a higher rate than e-commerce conversions,” since a form fill is a lower-effort action than a completed purchase. That framing matters for anyone comparing this report against a different one. A retailer benchmarking against the roughly 40% B2B figure would be comparing against the wrong curve entirely; the e-commerce numbers, topping out under 4% even at a 1-second load, are the relevant comparison.

Portent also flags a limit in its own dataset rather than smoothing over it: the B2C data in the 10-second range rests on a smaller sample of pages than the faster loads. For B2C it reports only a 1.5x gap against 10 seconds, not a rate, and this piece follows that same boundary rather than filling the gap.

Why we care#

Speed has barely moved since 2019. In the sample, 82% of B2B pages and 86% of B2C pages loaded in 5 seconds or less. B2B was unchanged from Portent’s 2019 run, and B2C rose from 81%.

Site type changes what “good” looks like. A team running an e-commerce checkout should not benchmark its conversion rate against a lead-generation site’s, and should not expect the same percentage-point stakes. The multiplier, not the absolute rate, is the number worth carrying into a business case for a performance budget.