---
id: howto-css-three-columns
title: "How To - Three Column Layout"
category: "Web_Recipes"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["3 column grid CSS float"]
duplicate_of: ""
source_trust_level: "B"
confidence_score: 0.81
created_at: 2026-07-04
updated_at: 2026-07-04
review_reason: ""
merge_history: []
tags: ["howto", "css", "w3schools", "layout", "float", "responsive"]
raw_sources: ["https://www.w3schools.com/howto/howto_css_three_columns.asp"]
applied_in: []
github_commit: ""
---

# [[HOWTO CSS Three Columns]]

## 🎯 한 줄 통찰 (One-line insight)
Beyond the standard equal-column formula (`width: 33.33%` for 3 equal float columns, same pattern as `[[HOWTO CSS Four Columns]]`), this recipe also shows UNEQUAL columns achieved by simply giving each column class its OWN explicit width (`.left, .right { width: 25%; } .middle { width: 50%; }`) instead of a shared class — proving that "N-column layout" isn't really about a fixed formula at all, just floats whose widths happen to sum to 100%, whether or not they're equal. [S1]

## 🧠 핵심 개념 (Core concepts)
- **Equal 3-column** — `.column { float: left; width: 33.33%; }` + `.row:after` clearfix. [S1]
- **Unequal 3-column** — separate classes with independently-set widths that still sum to 100%: `.left, .right { width: 25%; } .middle { width: 50%; }`. [S1]
- **Same responsive collapse pattern** — `@media (max-width: 600px) { .column { width: 100%; } }`, identical breakpoint value to the Two/Four column recipes. [S1]

## 📖 세부 내용 (Details)
- Equal columns: `.column { float: left; width: 33.33%; } .row:after { content: ""; display: table; clear: both; }`. [S1]
- Unequal columns: `.column { float: left; } .left, .right { width: 25%; } .middle { width: 50%; }`. [S1]

## ⚖️ 모순 및 업데이트 (Contradictions & updates)
없음 — 신규 레시피, 기존 문서와 모순되는 내용 없음.

## 🛠️ 적용 사례 (Applied in summary)
동일 폭 3열과, 25%/50%/25%로 나뉜 비대칭 3열 두 가지 예제가 원문에서 나란히 제시됨. [S1]

## 💻 코드 패턴 (Code patterns)
Equal vs. unequal 3-column float layout (CSS):
```css
/* Equal */
.column { float: left; width: 33.33%; }

/* Unequal -- widths just need to sum to 100% */
.left, .right { float: left; width: 25%; }
.middle { float: left; width: 50%; }
```

## ✅ 검증 상태 및 신뢰도
- **상태:** draft
- **검증 단계:** conceptual
- **출처 신뢰도:** B (W3Schools — widely used educational reference)
- **신뢰 점수:** 0.81
- **중복 검사 결과:** 신규 생성 (New discovery)

## 🔗 지식 그래프 (Knowledge Graph)
- **상위/루트:** [[W3Schools HOW TO]]
- **관련 개념:** [[HOWTO CSS Four Columns]], [[HOWTO CSS Two Columns]], [[HOWTO CSS Zig Zag Layout]]
- **참조 맥락:** CSS Layout & Positioning 섹션.

## 📚 출처 (Sources)
- [S1] W3Schools — How To - Three Column Layout — https://www.w3schools.com/howto/howto_css_three_columns.asp

## 📝 변경 이력 (Change history)
- 2026-07-04: Initial draft synthesized from the W3Schools "How To - Three Column Layout" recipe (Astra wiki-curation, P-Reinforce v3.1 format).
