A standard king size mattress is typically 76 inches wide by 80 inches long (about 193 cm by 203 cm).

Quick Scoop: King Size Basics

  • Standard king mattress: 76" x 80" (width x length).
  • In feet, thatā€™s roughly 6.3' x 6.7'.
  • Itā€™s the widest common mattress size and gives each of two sleepers about 38" of personal space.

Common King Variants (So You Donā€™t Mix Them Up)

  • California King: about 72" x 84" ā€“ narrower but longer than a standard king, popular with taller sleepers.
  • Other oversized ā€œkingsā€ (Texas, Wyoming, Alaskan) exist, but theyā€™re specialty sizes and much larger than the standard king.

Realā€‘World Feel (Mini Story)

Imagine two twin XL mattresses pushed together side by side ā€“ thatā€™s essentially the footprint of a standard king, which is why many adjustable beds use a split king layout. Couples who feel cramped on a queen often notice the extra 16" of width immediately when they upgrade to a king.

Room Size Tip

A king usually works best in a primary bedroom of at least about 12' x 12', so thereā€™s still walking space and room for nightstands. If your room is tighter, a queen may fit circulation and furniture better.

TL;DR:
Standard king size mattress = 76" x 80" (about 193 cm x 203 cm). Anything longer (like 72" x 84") is usually a California King, not a regular king.

Information gathered from public forums or data available on the internet and portrayed here.