WCAG text spacing checker

Enter every measurement in one consistent unit, such as pixels or points. The result reports each observed ratio, its required minimum, the corresponding minimum value, and an overall pass or fail. It is a focused numerical check for design reviews and automated tests, not a substitute for testing whether content remains usable when readers override spacing.

Measure all four values in one consistent unit

Start with the computed font size and the line-height, letter-spacing, and word-spacing values you want to evaluate. All four numbers must use the same unit because the checker divides every spacing measurement by the font size. Pixels are convenient when you copy computed styles from browser developer tools, but points, rems converted to numbers, or any other consistent length unit produce the same ratios. For example, a 16 pixel font paired with a 24 pixel line height produces a ratio of 1.5. A 1.92 pixel letter spacing produces 0.12, and a 2.56 pixel word spacing produces 0.16. Unit labels are intentionally not accepted: send numeric values after resolving CSS keywords, percentages, unitless line-height declarations, inherited values, and relative units to comparable measurements. The font size must be greater than zero; zero and negative font sizes cannot define meaningful relative spacing and are rejected. Other finite spacing values are evaluated as supplied, so a negative spacing value receives a failing ratio instead of being silently corrected.

Read the individual checks before the overall result

The response contains one check for line height, one for letter spacing, and one for word spacing. Each check repeats the supplied value, calculates its ratio to font size, states the WCAG-oriented minimum ratio, calculates the minimum absolute value for the supplied font size, and returns a Boolean pass result. The overall passes field is true only when all three individual comparisons pass. Values exactly on a boundary pass: a line-height ratio of 1.5, letter-spacing ratio of 0.12, or word-spacing ratio of 0.16 meets its respective threshold. The algorithm uses the numeric values directly and does not round before comparing, which avoids changing a result near a boundary merely for display. This output makes failures actionable. Instead of seeing only a generic rejection, a developer can identify the property below its target and compare the current value with minimum_value. Because the calculation is deterministic and has no network dependency, identical JSON input always produces identical JSON output in a browser, build pipeline, or API integration.

Use the result as a focused adjustability check

WCAG 1.4.12 is about preserving content and functionality when users apply specified text-spacing overrides. This calculator checks whether the three supplied measurements reach the ratios associated with line height, letter spacing, and word spacing; it does not inspect a page, rewrite CSS, or prove that a layout tolerates user overrides. A complete accessibility review should still apply the relevant spacing changes in a real browser and look for clipped text, hidden controls, overlaps, truncated labels, broken dialogs, and lost content. Paragraph spacing is another part of the success criterion, but it is outside this capability because the declared input covers only line height, letter spacing, and word spacing relative to font size. Use the numerical result to catch obvious token or stylesheet mismatches early, then use rendering tests for actual behavior. The browser version is useful during manual design review, while the API costs $0.002 per successful request and fits regression suites that evaluate resolved style values from components, themes, templates, or generated documents. Invalid input is rejected rather than converted or guessed.