About a few decades ago, the futon sizes were based on the unit of shaku (one shaku=36-38cm), which was originally used for the kimono sizes. Partly influenced by the Western culture, the futon sizes became later modified.
Here are the standard sizes of Japanese futon. They are based on standard fabric sizes. When we refer to the sizes, we use the sizes of the fabric habitually. They’ll get short 2 to 4 inch (5 to 10 cm) when cotton filling is stuffed.
Dimensions and names vary considerably around the world, with most countries having their own standards and terminology. Please check well before you order.
【The Fabric Size of Futon Mattress – Shikifuton】（unit：inch / cm）
Baby 33 x 51 / 85 x 130
Single 39 x 78 / 100×200
Single Long 39 x 82 / 100×210
Super Long 39 x 86 / 100×220
Semi Double 49 x 82 / 125×210
Double 55 x 82 / 145×210
Queen 62 x 82 / 160×210
It is said it fits the best if the length of futon is 12” (30 cm) longer than your height to place pillow.
【The Fabric Size of Futon Quilt – Kakefuton】（unit：inch / cm）
Baby 41 x 53 / 105 × 130
Single 59 x 78 / 150 × 200
Single Long 59 x 82 / 150×210
Semi Double 66 x 82 / 170×210
Double 74 x 82 / 190×210
Queen 82 x 82 / 210×210
Sizes of Futon Covers
When you buy a futon cover, be sure to measure the futon size that you are using.
Since the kake-futon (quilt) is usually thinner, you can use a futon cover which is similar in size to the kake-futon.
Since the shiki-futon (bottom mattress) has the thickness, you can use a little bigger futon cover with its dimensions 5 centimeters longer and wider.
As for a pillowcase, the size may vary depending on each item, so it might be good to buy a set of a pillow and a pillowcase.