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name: css-math-units description: "Explain, derive, and debug CSS math for measurement units, calc(), min(), max(), clamp(), custom properties, inheritance, em/rem scaling, percentages, viewport units, and box model formulas. Use when CSS dimensions compute unexpectedly, when mixing units, when building scalable spacing/type systems, or when reviewing box sizing and inherited values." license: MIT compatibility: Codex, Claude Code, and other Agent Skills-compatible clients. metadata: version: "0.1.0" displayName: CSS Math Units category: Frontend tags: frontend,css,units,layout,math

CSS Math Units

Use this skill to trace how CSS values become computed layout values. It is useful for unit conversion, inherited size multiplication, calc expressions, custom property math, and box model sizing.

Quick Start

1. Read guidelines.md to select the smallest relevant file set.
2. Load references/css-calculations/rules.md for implementation decisions.
3. Load references/css-calculations/examples.md when editing code.
4. Use workflows/debug-css-calculation.md for multi-step derivation or debugging.

Contents

Resource	Purpose
guidelines.md	Routes tasks to the right reference files
references/source-map.md	Book source and chapter/section traceability
references/css-calculations/knowledge.md	Core concepts and terminology
references/css-calculations/rules.md	Practical rules, guidelines, and exceptions
references/css-calculations/examples.md	Bad/good examples and refactoring approach
references/css-calculations/patterns.md	Reusable formula and implementation patterns
references/css-calculations/checklist.md	Review checklist and red flags
workflows/debug-css-calculation.md	Step-by-step workflow

Source

Derived from Math for Web Design by Paul McFedries, Chapter 3: Math basics for CSS. Citations are tracked in references/source-map.md.