Bigger PDP font (+4px) for older buyers: +4.17% revenue per visitor
Test run byDave DiederenSyntra Labs
Commentary byLiftArchiveOur analysis, not theirsRaising the product page font size by 4px lifted revenue per visitor by 4.17% in a test Dave Diederen ran for a store with an older audience. Conversion rate rose 1.71% and average order value rose 2.41%. A +2px version was also tested and landed close to the control.
- Revenue per visitor: $2.78 to $2.89 (+4.17%). The tool estimated about $83,356 extra per month.
- Conversion rate: 5.45% to 5.54% (+1.71%), a small lift.
- Average order value: $51.00 to $52.23 (+2.41%).
- The +2px variant was nearly flat: 5.47% conversion and $2.81 revenue per visitor.
- All confidence ranges crossed zero (revenue per visitor -4% to +13%), so this is not a clear-cut win.
The change
Same layout, product page text enlarged by 4px
Simplified mockup drawn by LiftArchive from the shared screenshots.
Control
The standard product page with the original body text size. Dave describes typical PDP copy as small 14px text.
Variant
The same product page with text sizes increased by 4px. A second variant used +2px.
Why it likely won
Our reading of the result, not the practitioner's claim.
- older shoppers often find small text hard to read, so bigger type lowers the effort to understand the product.
- larger text is easier to skim, and most visitors skim rather than read.
- the +4px step was large enough to be noticed, while +2px was not.
Caveats: The confidence ranges for every metric include zero, so the lift may be noise. It is one store with an older audience, and the run time and sample size were not shared.
Who ran it
Dave Diederen (@DaveDiederen) shared this test on X. The numbers and screenshots are theirs.
View the original post on X
How to run this test on your store
- Hypothesis
- If we increase product page font sizes by 4px, then revenue per visitor will rise because older shoppers can read and scan the page with less effort.
- Primary metric
- Revenue per visitor
- Guardrails
- Conversion rate
- Average order value
- Scroll depth on mobile
- Who should test it
- Stores selling to older customers that use small or low-contrast body text. Stores with young audiences or already large type will likely see less.
Questions
Does font size affect conversion rate?
It can. In this test a +4px increase lifted conversion 1.71% and revenue per visitor 4.17%, though the confidence ranges crossed zero.
How big should product page text be?
There is no single number. Here, +4px over the original beat both the control and a +2px version for an older audience.
Who benefits most from larger text?
Older shoppers, who often already enlarge text on their phones. That was the audience in this test.
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