Font size +4px for older shoppers: +3.82% revenue per visitor
Test run byDave DiederenSyntra Labs
Commentary byLiftArchiveOur analysis, not theirsIncreasing font size by 4px lifted revenue per visitor by 3.82% and conversion rate by 2.12% in Dave Diederen's test for a brand with older customers. A +2px version landed between the two, a little ahead of control. The ranges were wide, so this is a small, uncertain lift.
- Revenue per visitor (+4px vs control): +3.82% ($1.14 to $1.19). Positive, but the range ran from -22% to +38%.
- Conversion rate (+4px vs control): +2.12% (2.96% to 3.02%). A small gain, also with a wide range.
- Average order value (+4px vs control): +1.66% ($38.68 to $39.32).
- The +2px variant scored 2.99% conversion and $1.16 revenue per visitor, between control and +4px. Bigger text did a little better at each step.
The change
Same layout with all text enlarged; +2px and +4px variants were tested.
Simplified mockup drawn by LiftArchive from the shared screenshots.
Control
The store's original text size.
Variant
Two variants ran against control: one with text 2px larger and one with text 4px larger. Nothing else on the page changed.
Why it likely won
Our reading of the result, not the practitioner's claim.
- many older shoppers struggle with small text, so making it easier to read lowers effort at every step of the visit.
- the steady step from control to +2px to +4px hints at a real effect, even though each result alone is weak.
- design trends favour small, clean type, which can quietly work against an audience whose eyesight is not what it was.
Caveats: Sample size, test length and confidence were not shared, and every range crossed zero by a wide margin. Dave Diederen says it has won across multiple brands, but only this one result was shown.
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 the site's font size by 2-4px, then older visitors will buy more because the pages become easier to read.
- Primary metric
- Revenue per visitor
- Guardrails
- Average order value
- Mobile scroll depth
- Add to cart rate
- Who should test it
- Stores where a large share of buyers are 50 and over. For younger audiences on mobile, bigger text mainly pushes content down and may not help.
Questions
Does a bigger font size increase conversion?
For this older audience, a +4px font lifted conversion by 2.12% and revenue per visitor by 3.82%. The ranges were wide, so treat it as a likely small gain.
How much should I increase font size?
Dave Diederen tested +2px and +4px against control. The +4px version did best, and +2px came out a little ahead of control.
Is font size an accessibility or a conversion change?
Both. Making text easier to read helped older shoppers buy in this test.
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