CSS単位・カラーコンバーター

CSSカラーと単位の理解

HEX、RGB、HSLカラーフォーマット

CSSは複数のカラーフォーマットをサポートしています。

<strong>RGB</strong>は各チャンネルに0〜255の10進数値を使用します。

<strong>HSL</strong>はデザイナーにとって最も直感的です。

CSS Named Colors

CSS provides 147 named colors like coral, steelblue, and rebeccapurple. While convenient for prototyping, named colors offer limited precision. Converting a CSS color name to HEX or RGB gives you exact values you can fine-tune for production use.

印刷デザインのCMYK

<strong>CMYK</strong>は印刷の標準カラーモデルです。

デザインツールのHSV

<strong>HSV</strong>はPhotoshop、Figma、Sketchのネイティブカラーモデルです。

OKLCH — CSS Color Level 4

OKLCH (Lightness, Chroma, Hue) is the modern perceptually uniform color space introduced in CSS Color Level 4. Unlike HSL, OKLCH ensures that colors with the same lightness value actually appear equally bright to the human eye. It's supported in all modern browsers and is becoming the preferred format for design systems that need consistent, predictable color palettes.

LCH — CIE LCH Color Space

LCH (Lightness, Chroma, Hue) is the cylindrical representation of the CIELAB color space. It provides perceptually uniform color differences, meaning equal numerical changes produce visually equal differences. LCH is supported in CSS Color Level 4 via the lch() function and is widely used in color science, print workflows, and advanced design systems.

LAB — CIELAB Color Space

CIELAB (L*a*b*) is a device-independent color space that models human vision. L represents lightness (0–100), while a and b represent color-opponent dimensions (green–red and blue–yellow). LAB is the foundation for Delta E color difference calculations and is essential for color matching, print proofing, and scientific color analysis.

HWB — Hue Whiteness Blackness

HWB (Hue, Whiteness, Blackness) is a CSS Color Level 4 format designed to be more intuitive than HSL. You start with a hue, then add whiteness to lighten and blackness to darken. It's supported via the hwb() function in modern browsers and is particularly useful for creating tints and shades without complex math.

Tailwind CSS Colors

Tailwind CSS ships with a comprehensive color palette organized by name and shade (e.g., blue-500, rose-400). Converting Tailwind color classes to HEX codes is essential when integrating Tailwind designs with external tools, creating custom themes, or working with design tools that require hex values.

PX vs REM: CSS単位の解説

<strong>ピクセル(PX)</strong>は絶対単位です。

ピクセルを16で割ってREM値を求めます。

<strong>EM単位</strong>はルートではなく親要素のフォントサイズに相対的です。

• 1rem = 16px (default browser setting)
• 1em = parent font-size (context-dependent)
• 0.75rem = 12px — common for small/caption text
• 1.25rem = 20px — common for subheadings
• 2rem = 32px — common for section headings

なぜCSSコンバーターを使うのか？

手動での変換は面倒でエラーが起きやすいです。

• Instant results — paste a value and get the converted output immediately, no formulas needed.
• Copy-ready output — every result includes a one-click copy button with properly formatted CSS syntax.
• Color preview — see a live swatch of the converted color to visually confirm accuracy.
• No installation — works in any browser, on any device. No extensions, downloads, or signups.
• Developer-friendly — shareable URLs with pre-filled values for easy team collaboration.

Common CSS Conversion Workflows

• Design handoff: Figma and Sketch export colors as HEX. Convert to RGB or HSL if your codebase uses those formats.
• Dark mode generation: Take your light-mode HSL palette, adjust lightness values, and convert back to HEX.
• Accessibility checks: Convert colors to RGB to calculate contrast ratios using the WCAG luminance formula.
• Legacy migration: Convert pixel-based layouts to rem-based responsive systems during refactors.
• Cross-browser debugging: Quickly convert colors to match your source code format.

Supported Conversions