King-size mattress (US) Size Guide

A US (Eastern) king mattress is 76 x 80 inches, or 193 x 203 cm (1930 x 2032 mm). It is the widest common mattress size, effectively two twin XL mattresses side by side, and it needs a large bedroom to sit comfortably.

This guide covers the exact king dimensions, how they compare to a California king and a queen, how much floor space the bed needs, and how much a king mattress weighs.

Quick Answer: How Big Is a King Mattress?

A standard (Eastern) king is 1930 mm wide and 2032 mm long (76 x 80 in, 6 ft 4 in x 6 ft 8 in). Thickness is usually 250 – 350 mm. It weighs roughly 30 – 60 kg depending on construction.

King Mattress Dimensions at a Glance

• Size: 1930 x 2032 mm / 193 x 203.2 cm / 76 x 80 in
• Per person: about 965 mm (38 in) of width each, the same as a full twin bed each
• California king: 1829 x 2134 mm (72 x 84 in), 101 mm narrower but 102 mm longer
• Split king: two pieces of 965 x 2032 mm (two twin XL), for adjustable bases
• Minimum room: about 3.4 x 3.4 m to allow walkways on both sides and the foot

What Does a King Mattress Look Like in Size?

The sleep surface is about 1.93 m wide and 2.03 m long, almost square. Two adults each get roughly a twin bed’s width, and there is room for a child or a pet without crowding. It covers about the floor area of a small bathroom.

6 Everyday Comparisons for a King Mattress

1. A queen mattress (1524 x 2032 mm) is 406 mm (16 in) narrower and the same length; a king has about 26% more sleep area.
2. A California king (1829 x 2134 mm) is 101 mm narrower but 102 mm longer, better for tall sleepers.
3. Two twin XL mattresses (965 x 2032 mm each) side by side equal a standard king exactly.
4. A standard interior door (813 x 2032 mm) is the same length and about 42% of the width.
5. A 3-seat sofa (about 2000 mm wide) is close to the king’s length.
6. A queen and a twin side by side (1524 + 965 = 2489 mm) are wider than a king by 559 mm.

King Mattress Size in Different Units

How Much Room Does a King Bed Need?

With the frame overhang (50 – 150 mm each side) and a 600 mm (2 ft) walkway on the sides and foot, the practical minimum bedroom is about 3.4 x 3.4 m. For bedside tables and a clear path to a wardrobe, aim for 4.0 x 4.3 m. A king often will not fit up a tight staircase in one piece, which is why split kings exist.

How Much Does a King Mattress Weigh?

A king is always a two-person carry, and the near-2 m width makes it awkward through standard 762 mm doorways, which usually means turning it on edge.

Common Mistakes When Comparing King Mattress Dimensions

1. Assuming a California king is bigger overall. It is narrower than a standard king; it just trades 4 inches of width for 4 inches of length.
2. Thinking a king is much longer than a queen. They are the same 80 in length.
3. Forgetting the doorway problem. A 1930 mm mattress will not go through a 762 mm door flat.
4. Confusing “king” internationally. A UK king is about 150 x 200 cm, closer to a US queen; a UK super king is about 180 x 200 cm.
5. Sizing the room to the mattress only. Walkways and frame overhang add roughly a metre to each dimension.

Frequently Asked Questions

How big is a king mattress in cm?

193 x 203 cm.

How big is a king mattress in feet?

6 ft 4 in wide by 6 ft 8 in long.

Is a king or a California king bigger?

Neither is simply bigger. A standard king is wider; a California king is longer.

How much bigger is a king than a queen?

16 inches (406 mm) wider; the length is the same.

What size room do I need for a king bed?

At least 3.4 x 3.4 m, comfortably 4.0 x 4.3 m.

How much does a king mattress weigh?

About 30 – 60 kg depending on construction.

Final Takeaway

A US king mattress is 76 x 80 in (193 x 203 cm), weighs 30 – 60 kg, and needs a bedroom of at least about 3.4 x 3.4 m. It is the same length as a queen but 16 inches wider, it equals two twin XL mattresses side by side, and a California king trades width for extra length rather than being larger overall.