Why Your CSS Should Use Rem Units and How to Convert From Pixels

Every CSS value you write in pixels is a decision to ignore user accessibility preferences. That sounds harsh, but it's technically accurate. When a user sets their browser's default font size to 20px instead of the standard 16px, they're telling every website: "I need larger text." Rem units respect this preference. Pixel units do not. The conversion 1rem = the root element's font size (usually 16px by default). To convert: rem = px / 16. That's it. Here's a reference table for the most common values: 10px = 0.625rem 12px = 0.75rem 14px = 0.875rem 16px = 1rem 18px = 1.125rem 20px = 1.25rem 24px = 1.5rem 28px = 1.75rem 32px = 2rem 36px = 2.25rem 40px = 2.5rem 48px = 3rem 64px = 4rem Where to use rem, where to keep pixels Use rem for: Font sizes (always) Spacing and padding on text-adjacent elements Max-widths for readable text containers Media query breakpoints (though these always use the browser default regardless) Keep pixels for: Borders (a 1px border should stay 1px) Box shadows V