- From: 張俊芝 via GitHub <noreply@w3.org>
- Date: Tue, 27 Jan 2026 05:25:58 +0000
- To: public-css-archive@w3.org
Thank you for your feedback. However, there is one common misunderstanding about CSS units that I’d like to clarify: > I believe touch targets should be specified in a _physical_ unit like `mm`, possibly within `min()`, `max()` or `clamp()` together with an _optical_ unit like `px`. `mm` is not a physical unit on screens either. Contrary to what many believe, `mm` and `px` are either both physical (e.g., in print media) or both non‑physical (e.g., on screens). On screens, all absolute length units—`px`, `mm`, `cm`, `in`, etc.—are anchored to the reference pixel, not to actual physical measurements. Their ratios are fixed by definition: `1in = 96px = 2.54cm`, thus `1mm = (96px / 25.4) ≈ 3.7795px` in all media. Therefore, combining `px` and `mm` with `clamp()` or similar functions does not solve the problem, because their relationship never changes across media. -- GitHub Notification of comment by Zhang-Junzhi Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/13398#issuecomment-3803187518 using your GitHub account -- Sent via github-notify-ml as configured in https://github.com/w3c/github-notify-ml-config
Received on Tuesday, 27 January 2026 05:25:58 UTC