Standard bed sizes are based on standard mattress sizes, which vary from country to country. Bed sizes also vary according to the size and degree of ornamentation of the bed frame. Dimensions and names vary considerably around the world, with most countries having their own standards and terminology. In addition, two mattresses with the same nominal size may still have slightly different dimensions, due to manufacturing tolerances, amount of padding, and support type. In almost all territories, standard beds are rectangular. Notably, a square shape (i.e. 200 cm × 200 cm (79 in × 79 in)) allows the user to put on sheets without having to consider its lengthwise orientation. More specialised shapes may be obtained by special order (for example circular beds). Mattress sizes may differ from bedding sizes.

The choice of an appropriate bed size may depend on:

Buying common sizes may give an increased availability for buying compatible mattresses and bedding.

When changing to a different bed size, different sized sheets may be required, although many sheets today are stretchy and have some leeway built in to fit several bed sizes.

All else being the same, larger beds also tend to be more expensive.

Some recommend that the bed size should be at least 15 cm (6 in) longer than the height of the person sleeping in it, i.e. 200 cm (79 in; 6 ft 7 in) long for a 185 cm (6 ft 1 in) tall person.^[1] Some recommend that a double bed should allow two persons enough room to both lie on their back with their hand behind their head without their elbows touching.^[1][86]

Naming standards on different bed sizes and their corresponding actual measurements can vary across national standards.

Examples of such nomenclature are names like "Single", "Double", "Queen" or "King size".

Sometimes the naming standards are further divided by adding adjectives such as "Narrow", "Wide", "Extra Wide", "Long", "Extra Long" and so on, which also can vary across national standards.

For example, a King size bed may measure (in width by length):

For these reasons, European bed sizes are instead nowadays only given in centimetres (width by length).

Europe may traditionally have had more variations in national bed size standards than any other part of the world,^[11] but in the recent years a few sizes have become more common than others, and in some sense becoming de facto continental European standards, possibly due to international trade. Except the UK and Ireland, bed sizes are defined in centimetres in all European countries. Approximate unit conversion equivalents are shown alongside here.

Today, the most common widths sold by pan European retailers are:

Other sizes are also available in select European countries (i.e. 80 or 140 cm (31 or 55 in)), but the widths listed above are the most common when looking at the European market as a whole.

Today, the 200 cm (79 inches) length is the most common bed length sold by pan European retailers.

Lengths of 210 or 220 cm (83 or 87 inches) are often also available by special order.

The longer beds are intended for taller persons,^[13] and as a rule of thumb 210 cm long beds may be recommended to persons 190 cm (6 ft 3 in) or taller, while 220 cm beds are recommended for persons over 200 cm (6 ft 7 in) tall.^[14]

In France, single size beds are usually 90 by 190 centimetres (35 by 75 inches).

The most common sizes for double beds are:

Due to the popularity of imported beds (especially from IKEA), the 200 centimetres (79 inches) length is becoming more common across all bed sizes.

In Italy, beds are classified by name and use the term piazza as in "one place" Standard sizes are:^[15]

Due to the popularity of imported beds (especially from IKEA), the 200 centimetres (79 inches) length is becoming more common across all bed sizes.

These sizes are for Germany, Poland, Belgium, Netherlands, Luxembourg, Norway, Sweden, Denmark, Iceland, Finland, Estonia, Latvia, and Lithuania.

There are some variations between different countries, but these are the most common sizes:

Note: 120 and 140 cm-wide (47-and-55-inch) beds are sometimes considered as "wide" single-beds, and sometimes as "narrow" double-beds.

In Portugal, the most common sizes for beds are:

In Spain, standardised lengths are 180, 190 and 200 centimetres (71, 75 and 79 inches), with 190cm being the most common.

Standardised widths are 80, 90, 105, 120, 135 or 150 centimetres (31, 35, 41, 47, 53 or 59 inches).

The most common bed sizes are:

In the United Kingdom and Ireland, beds are measured according to the size of mattress they hold, not the dimensions of the bed frame itself; bed sizes are not standardised and may differ between manufacturers.^[18][19] Below are the typical bed sizes from the National Bed Federation, which is the trade association for the majority of British and Irish bed manufacturers and their suppliers.^[20] Most manufacturers use a standard defined in feet and inches with the metric indicators not being exact equivalents.^[18] There can legally be a tolerance of up to ±2 centimetres (0.8 in) in quoted measurements and the size of the mattress itself.^[21]

Less commonly used sizes include:

As well as UK standard sizes, common European sizes are also sometimes found in the UK from imports and IKEA.^[19][24] The typical length of an IKEA and other European mattresses is 79 in (200 cm), whereas UK lengths vary depending on the width of the mattress, being usually either 75 or 78 in (191 or 198 cm).^[25] Due to the popularity of imported beds (especially from IKEA), the 200 centimetres (79 inches) length is becoming more common. In 2015, IKEA also started offering UK sizes in Britain alongside their standard European sizes.^[26]

While many companies in the UK offer custom-made bed making services, most mass-produced bed linens, bed frames and mattresses fit only the standard bed sizes above.

The sizes of mattresses use non-numeric labels such as a "king" or "full", but are defined in inches.

Historically most beds were "twins" or "doubles" but in the mid-1940s larger mattresses were introduced by manufacturers.

These were later standardised as "queen" and "king", and first made a significant impact on the market in the 1950s and 60s.^[28] Standard mattress depth ranges from the "standard" size of 9 inches (23 cm) to "high contour" of up to 13 inches (33 cm).

Below are the standard ISPA widths and heights in the United States and Canada,^[29][30]. U.S. bed sizes usually have a length of either 74 or 80 in (188 or 203 cm), while UK bed sizes usually have a length of either 75 or 78 in (191 or 198 cm). Widths also differ between the U.S. and UK standards.

Less common sizes include:

Bedding in the United States must state the type of bed it is intended for, in addition to the dimensions in both inches and centimetres.^[34]

The following bed sizes are available in Australia.

The following bed sizes are available in New Zealand.

In South Africa, bed sizes have standard lengths of either 188 or 200 cm (74 or 79 in),^[36] with the latter being called XL variants.

XL mattresses have the same widths as their non-XL counterparts.^[37] The 200 cm XL length is recommended for persons over 183 cm (6 ft) tall.^[38]

In India, the regulation standard has the following sizes available,

In China, the regulation standard has the following sizes available:^[39]

In practice, bed sizes are usually categorized by the width.

The length is typically 200 cm, but this may vary.

The most common sizes are:

There are also other bed sizes available, but they are less common.

In Indonesia, the standard length is 200 cm (79 in). The following standard sizes are commonly available in Indonesia:

The following bed sizes are available in Singapore and Malaysia:

Standard Japanese bedding sizes are described in the standard JIS S 1102:2017 Beds for domestic use by the Japanese Standards Association.^[40]