Japanese Mattress Sizes: Futon, Single, and Semi-Double Explained

The Japanese Mattress Sizing System

Japan uses its own mattress sizing standard developed alongside the postwar boom in Western-style beds. The dimensions are set by the Japan Bedding Industry Association (JBIA) and differ from both US and EU sizes. Japanese mattresses are consistently 5 centimeters (about 2 inches) shorter than their European counterparts at the same width -- a 195cm standard length versus the European 200cm.

Japanese Mattress Size Chart with US Comparisons

The Semi-Double: Japan's Most Popular Size

The semi-double (120x195cm) is uniquely Japanese. It is the dominant size in urban Japanese apartments because it fits efficiently in compact rooms -- it is 20cm narrower than a standard double but still comfortable for a single adult. This size has no US equivalent, which creates the most significant compatibility problem for Japanese buyers moving to the US.

If you own a Japanese semi-double mattress and are moving to the US, the options are: sell it in Japan (it holds good resale value), ship it and use it on the floor with a tatami mat, or purchase a US twin or full-size frame and accept the dimensional mismatch.

Japanese Futon Sizes (Shikibuton)

Traditional Japanese floor futons (shikibuton) use different naming conventions than Western beds:

• Single shikibuton: 100x210cm (39x83in) -- longer than a standard Western mattress to allow for pillow placement
• Double shikibuton: 140x210cm (55x83in)
• King shikibuton: 180x210cm (71x83in)

Shikibuton are 3-6cm thick and designed to be rolled or tri-folded and stored in a closet (oshiire) each morning to preserve floor space. Using a shikibuton on a Western platform bed is possible but misses the cultural rationale.

For more on mattress construction differences, see our guide to mattress layers and our comfort layer breakdown.

When Japanese Mattresses Are Used in US Frames

The most common scenario: someone buys a Japanese brand mattress (Airweave, Nishikawa, Magniflex Japan) during a stay in Japan and ships it to the US. The practical issues:

1. Length gap: Japanese mattresses are 195cm (76.8in). US queen frames are 80 inches. A 3.2-inch gap appears at the foot of the bed.
2. Width overhang: Japanese queens at 63 inches are 3 inches wider than a US queen frame (60in), meaning the mattress overhangs on each side.
3. Fitted sheets: US queen sheets will be loose on a Japanese queen. Order custom or use IKEA sheets.

Our mattress support core guide explains how Japanese and US mattresses differ in construction, and our sleep environment checklist covers other setup considerations.

Frequently Asked Questions

What is a Japanese semi-double mattress in US terms?

A Japanese semi-double is 120x195cm (47x77in). It is wider than a US twin (38in) but narrower than a US full/double (54in). There is no direct US equivalent.

Can a Japanese futon be used on a Western bed frame?

Traditional Japanese shikibuton futons are 3-4 inches thick and meant to be rolled up and stored. They can rest on a Western platform frame but lack support for back health over time. A tatami base is optimal.

Are Japanese mattresses smaller than US mattresses?

Generally yes. The Japanese single (100x195cm / 39x77in) is close to a US twin but 3 inches shorter. The Japanese queen (160x195cm) is slightly wider but 5 inches shorter than a US queen.

What is the standard Japanese queen size in inches?

A Japanese queen is 160x195cm, or approximately 63x77 inches. A US queen is 60x80 inches -- so the Japanese queen is 3 inches wider but 3 inches shorter.

Do Japanese mattress brands like Nishikawa or Airweave fit US frames?

Airweave and Nishikawa sell models sized for US markets with US-standard dimensions. Their Japan-market products use Japanese sizing and will not fit standard US frames without gaps.