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About this tool
Turn font size, line height and padding into a button box, then check it against WCAG 2.5.8, WCAG 2.5.5, Apple HIG and Material target sizes.
The Button Minimum Size Spec Generator computes the real rendered box of a button from its font size, line height, padding, border and icon, then checks that box against four target-size rules: WCAG 2.2 SC 2.5.8 (24 by 24 CSS pixels, Level AA), WCAG 2.1 SC 2.5.5 (44 by 44, Level AAA), the Apple Human Interface Guidelines 44 by 44 pt tap target, and Material Design's 48 by 48 dp touch target. It also models the SC 2.5.8 spacing exception, which lets an undersized target conform when adjacent targets are far enough apart, and reports the exact padding needed to clear whichever standard you are aiming at.
Open Button Minimum Size Spec Generator on AltFTool — it loads instantly in your browser.
Provide your input — an image, text, or data.
Let the tool analyze or generate the result.
Review, refine, and reuse the output wherever you need it.
Adds line-height times font-size to padding and border on both edges, the way the browser does.
Applies the real SC 2.5.8 test - a 24 pixel circle on each target's bounding box must not intersect its neighbour's.
Reports the exact per-edge padding needed to reach 24, 44 or 48 pixels rather than leaving you to solve for it.
24 by 24 CSS pixels under WCAG 2.2 SC 2.5.8 at Level AA, and 44 by 44 under WCAG 2.1 SC 2.5.5 at Level AAA. Apple's Human Interface Guidelines ask for 44 by 44 pt and Material Design for 48 by 48 dp, so 48 is the practical target if you want to satisfy all four.
An undersized target still conforms if a 24 CSS pixel diameter circle centred on its bounding box does not intersect the circle of any adjacent target. For two equal targets in a row that reduces to a simple test: target size plus the gap between them must be at least 24 pixels.
With the standard border-box model: line-height multiplied by font-size, plus the top and bottom padding, plus the top and bottom border. A 16px label at line-height 1.25 with 8px padding and a 1px border is 20 + 16 + 2 = 38 pixels tall, which misses the 44 pixel AAA target by six.
Yes - the target-size rules apply to both dimensions, so a tall but very narrow button can still fail. Width here is estimated from an average glyph advance, which varies by typeface, so measure the real string when the width is close to the threshold.