How to Use This Tool
See how large source artwork text becomes in a narrow thumbnail preview. Text that looks large in a 1280-pixel editor can become unreadably small when the thumbnail is scaled into a mobile list.
Why Mobile Thumbnail Text needs more than a raw total
Proportional scaling exposes the actual display height without pretending every YouTube surface uses one fixed preview width. For this page, the useful comparison is displayed text height, not whichever input happens to be largest. The Mobile Thumbnail Text result answers the decision in the heading and should not be reused as a score for a different workflow.
The exact Mobile Thumbnail Text formula
Displayed text height equals source text height multiplied by preview width divided by source artwork width. The visible fields are Text height in source artwork, Source thumbnail width and Observed preview width. For Mobile Thumbnail Text, read each printed unit before entry and make the values describe one transaction, cohort or reporting window. If those scopes differ, the displayed displayed text height may be arithmetically valid but operationally meaningless.
Interpreting displayed text height
Measure the target surface, calculate the displayed height and test the exported image at that physical size before publishing. The ten-percent comparison is deliberately narrow: it tests the influence of text height in source artwork and is neither a forecast nor a confidence interval. Preserve the values used, their dates and the resulting decision so a later reviewer can reproduce why Mobile Thumbnail Text supported the choice.
What this Mobile Thumbnail Text model leaves out
The model does not measure font weight, contrast, device density, vision, compression or the surrounding visual clutter. That is where Mobile Thumbnail Text stops being trustworthy. If an excluded factor could reverse displayed text height, extend the model explicitly or use the authoritative account system instead of hiding the factor inside an unexplained adjustment.
Evidence and independent verification
The reference reviewed for Mobile Thumbnail Text is YouTube Help — Add video thumbnails. YouTube Help — Add video thumbnails supports the named definition or rule but does not supply private values for displayed text height. Before acting on the result, reconcile the worked example with the relevant dashboard, invoice, export or measurement.
Private, reproducible calculation
Mobile Thumbnail Text runs its arithmetic in the current browser tab and requests no login or API key. That keeps the Mobile Thumbnail Text inputs away from the site's calculation server, while leaving the user responsible for detecting stale data or a changed platform rule. When an assumption changes, reopen YouTube Help — Add video thumbnails and rerun the saved Mobile Thumbnail Text scenario.
Sources & assumptions
Tool Spec v2 · verified 2026-08-22. Platform rules and fees can change; the editable inputs remain authoritative for your account.
Official references
- YouTube Help — Add video thumbnails (checked 2026-08-22)
Model assumptions
- Every input covers the same reporting period or cohort.
- The model does not measure font weight, contrast, device density, vision, compression or the surrounding visual clutter.
- The calculator uses only the visible fields and does not fetch account data.
