CSS Unit Converter

CSS Unit Converter - px, rem, em, % Calculator

🎨 Convert between CSS units: pixels (px), rem, em, percentages (%), points (pt), and viewport units (vw, vh). Essential tool for responsive web design and development.

CSS Unit Types

• Absolute Units: px, pt, cm, mm, in - fixed size regardless of context
• Relative Units: rem, em, %, vw, vh - scale based on parent or viewport
• Font-relative: rem, em, ch, ex - based on font size
• Viewport-relative: vw, vh, vmin, vmax - based on viewport dimensions

Unit Explanations

• px (pixels): 1px = 1 device pixel. Absolute unit, precise but not scalable.
• rem: Relative to root element (html) font size. 1rem = 16px by default.
• em: Relative to parent element font size. Can compound in nested elements.
• %: Relative to parent element's property. 100% = same as parent.
• pt (points): Print unit. 1pt = 1/72 inch ≈ 1.333px.
• vw: 1vw = 1% of viewport width. 100vw = full width.
• vh: 1vh = 1% of viewport height. 100vh = full height.

Common Conversions

• 1rem = 16px (default browser setting)
• 1em = 16px (if parent is 16px)
• 100% = parent element size
• 12pt = 16px (common in print)
• 1vw = 19.2px (on 1920px viewport)

62.5% Method

Set html { font-size: 62.5%; } to make 1rem = 10px. This simplifies calculations: 1.6rem = 16px, 2.4rem = 24px, etc.

Accessibility Considerations

• Use rem for fonts: Respects user's browser font size preferences
• Avoid px for fonts: Doesn't scale with user settings
• Use relative units: Makes designs accessible to zoom/magnification
• Test with different sizes: Check 200% zoom and large text settings

Responsive Design

Use rem for media queries: @media (min-width: 48rem) instead of 768px. This ensures breakpoints scale with user's font size preferences.

💡 Pro Tip: Modern best practice is to use rem for most sizing (fonts, spacing, breakpoints), px for borders and fine details, and % or viewport units for layouts. Avoid em for spacing as it can compound unexpectedly.