Convert between px, rem, em, %, vw, vh, pt, cm, mm, and in instantly. Click any value to copy.
Accessibility. When users change their browser's default font size (for vision impairment or preference), rem units scale proportionally — px stays fixed.
Consistency. 1rem always equals the root font size. Unlike em, it doesn't compound when nested. Set your base, and every rem value is predictable.
Best practice. Use rem for font sizes, spacing, and layout. Use px for borders, shadows, and fine details that shouldn't scale. Use %/vw/vh for responsive container widths.