Mattress Size Guide: From Single to Super King

Key takeaways

• UK mattress sizes run from small single (75 x 190 cm) up to super king (180 x 200 cm); always double-check that your bed frame matches these measurements.
• Allow at least 10–15 cm of extra length beyond the tallest sleeper, or consider longer options if someone is particularly tall.
• Children often sleep well on a standard single, but younger kids may appreciate junior-friendly options like an all-in-one inflatable bed and sleeping bag for trips and sleepovers, such as an official Bluey ReadyBed mattress and sleeping bag combo available from trusted retailers.
• Measure your room, including door swing and walkway space, before choosing a double, king or super king so the bed does not dominate the whole layout.
• Mattress depth varies; deeper designs can feel more luxurious but may sit higher on tall bed frames and affect how easy the bed is to get in and out of.

Understanding standard UK mattress sizes

UK mattress sizes follow fairly consistent dimensions, although a few centimetres of variation can occur between brands. Knowing the standard sizes makes it far easier to compare mattresses, choose matching bedding and check that your existing bed frame will work with a new mattress.

Here are the most common UK mattress sizes and their typical dimensions:

• Small single: 75 cm x 190 cm
• Single: 90 cm x 190 cm
• Small double: 120 cm x 190 cm (sometimes called a ‘three-quarter’ bed)
• Double: 135 cm x 190 cm
• King: 150 cm x 200 cm
• Super king: 180 cm x 200 cm

The width tells you how much side-to-side space you have, while the length determines how much room there is from your head to your feet. Many people focus on width for comfort, but for taller sleepers the extra 10 cm of length on a king-size or super king mattress can be just as important as the wider sleeping area.

How much space does each person really need?

It is easy to underestimate how much room you and your partner need to sleep comfortably. A useful rule of thumb is that each person should have at least as much width as their arm span, or at minimum around 70–75 cm of sleeping space. This helps reduce the chances of disturbing each other when you roll over or change position in the night.

On a standard double (135 cm wide), two adults effectively get only a little more space than a small single each. This can work for smaller adults or couples who like to sleep close together, but many people find a king-size (150 cm wide) or super king (180 cm wide) gives a more relaxed, less cramped feel. The extra 15–45 cm of width can make a noticeable difference if one partner is a restless sleeper or if you sometimes share the bed with children or pets.

For children, a single mattress usually provides more than enough room to move and grow. Younger kids and toddlers might start out in a small single or junior bed, and you can gradually move them up to a full single as they get taller. If you want something portable for sleepovers and trips, a compact all-in-one sleeping solution such as a kids’ inflatable mattress and sleeping bag combo can be extremely convenient compared with a full frame and mattress.

Small single and single mattresses: best for kids and narrow rooms

Small single mattresses (75 x 190 cm) are ideal for very compact rooms, box rooms and some bunk beds. They offer a narrower footprint than a standard single while still providing enough space for a child or smaller teenager to sleep comfortably. They are also useful if you need to fit two beds into a small guest room, for example two siblings sharing or twin beds for visitors.

Single mattresses (90 x 190 cm) are the go-to size for most children, teens and solo adult sleepers. They strike a good balance between comfort and space-saving, making them well suited to standard UK bedrooms. If you are equipping a child’s room, look for kid-friendly designs that provide appropriate support without being too firm, such as memory foam or Bonnell spring mattresses tailored for children’s bodies.

For younger children, you may not want to invest in an expensive adult mattress straight away. Affordable kid-specific mattresses can offer good support and durability while you wait to see how quickly they grow. You might also supplement a main mattress with portable options for holidays and sleepovers. For example, an inflatable kids’ bed with built-in sleeping bag can save space and storage while still giving youngsters a fun and comfortable place to sleep away from home.

Small double and double mattresses: flexible options for couples and guests

Small double mattresses (120 x 190 cm) sit between a single and a full double. They offer more width than a single for solo sleepers who like to spread out, or a cosy option for two smaller adults. They are popular in studio flats, compact guest rooms and student accommodation where floor space is limited but you want more than a single bed.

Double mattresses (135 x 190 cm) are widely considered the standard size for couples in the UK. They provide room for two adults to sleep side by side without taking up as much floor space as a king or super king. However, if either partner is tall or has a larger frame, a double can feel a little tight. If your bedroom layout allows, moving up to a king-size can significantly reduce the feeling of being bumped or disturbed during the night.

Double and small double sizes are also great for guest rooms. They give visiting couples adequate space without overwhelming the room. If the bed will be used only occasionally, you might balance cost and comfort by choosing a more affordable, durable design rather than the most luxurious model you can find. If your guest space doubles as a home office, mattress alternatives like sofa beds and futons are worth considering alongside fixed-bed sizes.

King and super king mattresses: for maximum space and comfort

King-size mattresses (150 x 200 cm) are wider and slightly longer than a double. The extra length is particularly helpful if one or both sleepers are tall, as it offers around 10 cm more legroom. The extra width also reduces partner disturbance and creates a more luxurious feel. If you have a medium to large bedroom, a king-size can be an excellent balance between comfort and practical space.

Super king mattresses (180 x 200 cm) are the widest standard UK size, providing an expansive sleeping surface that feels almost like two single beds side by side. They are ideal for larger bedrooms, couples who value personal space, and families who often have children or pets joining them. Super king beds can transform the feel of a master bedroom, but you do need to allow plenty of surrounding space for bedside tables, walking routes and storage.

Before committing to a king or super king mattress, measure your room carefully. Check not only the floor space but also doorways, stairs and tight corners along the delivery route. A mattress that suits your body size and sleep style is only useful if it can actually be carried into the room without difficulty. If you are unsure whether bigger is practical, you could also explore split-base bed frames, which are easier to manoeuvre than one solid base.

Mattress length for tall sleepers

If you or your partner are tall, mattress length becomes just as important as width. A standard UK mattress length of 190 cm may be too short for people around or above 6 feet tall, especially if you prefer to sleep fully stretched out or on your back. Ideally, you want at least 10–15 cm of extra length beyond your height to avoid your feet hanging over the edge.

King and super king mattresses in the UK usually add 10 cm of length (taking them to around 200 cm). This extra room can make a noticeable difference if you are tall. Some specialist bed manufacturers also offer custom extra-long mattresses, though you will need to check dimensions carefully and ensure bedding is easy to source. Even if you are not notably tall, a slightly longer mattress can still feel more generous and less restrictive.

Remember that headboards and footboards can affect usable length. A thick, padded headboard may slightly reduce how far up the mattress you can comfortably rest your pillow, while a solid footboard can make the bed feel shorter for very tall people. If you are selecting both a new bed frame and mattress, consider an open-ended or low footboard design if legroom is a priority.

Mattress depth and comfort

While most of the focus is on mattress width and length, depth (or thickness) also matters. Typical UK mattresses range from around 15 cm to over 30 cm in depth. Deeper mattresses often include extra comfort layers, more substantial spring systems or thicker foam, which can feel more cushioned and luxurious. However, thicker is not always better for everyone.

A very deep mattress on a high bed frame can make the bed awkwardly tall, especially for children, shorter adults or anyone with mobility concerns. Getting in and out may feel more like climbing up, and it can be harder to sit comfortably on the edge. On the other hand, a shallower mattress on a low platform bed can make the bed feel very close to the floor, which some people love and others find uncomfortable.

For children, a moderate depth is usually ideal: deep enough to offer proper cushioning and support, but not so high that it becomes difficult to climb in and out. A dedicated kids’ memory foam mattress, for example, might sit around 20 cm deep and offer supportive, contouring comfort without making the bed overly tall. Options like a children’s single memory foam mattress or a Bonnell spring kids’ mattress can give a good sense of typical depth and construction aimed at younger sleepers.

Tip: When checking mattress depth, look at the total sleeping height – mattress plus bed frame. Ideally, you want the top of the mattress to sit roughly at knee height so it feels natural to sit and stand up.

How to measure your bed frame for the right mattress size

Before ordering a new mattress, it is crucial to confirm the size of your existing bed frame. Do not rely solely on what you think the size is; measure it carefully so you avoid gaps, overhangs or a mattress that simply will not fit. You only need a tape measure and a couple of minutes.

First, measure the internal length and width of the bed frame where the mattress sits, from inner edge to inner edge. Ignore decorative side rails or headboard thickness – you want the actual support area, not the outer footprint. Compare these measurements to the standard mattress sizes. A small variation of a centimetre or so is usually fine, but bigger discrepancies may cause problems with support or stability.

Next, consider whether your bed uses slats, a solid base or a sprung base. Slatted bases should have slats spaced closely enough for your chosen mattress type; some foam and hybrid mattresses specify maximum slat gaps in their care instructions. You can explore more about different mattress constructions in this guide to memory foam versus hybrid mattresses. Ensuring good support helps maintain comfort and prolong the life of your mattress.

Planning mattress size around your bedroom layout

Even if a mattress technically fits between the walls of your room, it still needs to work with doors, wardrobes and walking space. A bed that is too large for the room can make everything feel cramped and awkward. When choosing between, say, a double and a king-size, sketch your room or use a tape measure to mark out where the mattress will sit.

Allow at least 60 cm of clear walkway space along the sides of the bed where you will be getting in and out. Check that wardrobe doors and drawers can open fully without hitting the mattress or bed frame. Pay attention to windows, radiators and plug sockets too; you want bedside tables and lamps to be easy to reach without blocking airflow or access.

In small rooms, a single or small double can free up valuable floor area for a desk, storage or play space. In larger master bedrooms, a king or super king may actually make the room feel more balanced and less empty. Think about how you use the space: if you often relax, read or work on the bed, extra width can be especially welcome.

Choosing mattress sizes for children and teens

Picking the right mattress size for a child involves balancing current comfort, future growth and available room space. Younger children can sleep well on smaller beds, but if you have the space, moving to a full single early on can avoid needing to replace the bed too soon as they grow taller.

For very young children transitioning from a cot, a small single or junior bed can feel cosy and secure. As they move into primary and secondary school, a standard single gives more room to stretch out and can easily last into their teenage years. If the bedroom is spacious and you expect them to stay in the same room for a long time, you might even consider a small double so they have extra space to relax, read and host sleepovers.

Aside from everyday sleep, it is worth thinking about occasional needs. Portable solutions such as an inflatable ready bed with integrated sleeping bag are excellent for sleepovers and holidays, as they pack away compactly yet still feel familiar and fun for children. For their main bed, a supportive single mattress designed with kids in mind, such as a single memory foam kids’ mattress or a Bonnell spring children’s mattress, can give the right mix of comfort and support during growth years.

Insight: Children do not just grow taller – their sleep habits and study needs change too. Leaving a little extra mattress width or length can help their bed stay comfortable and practical into their teenage years.

Matching mattress size to mattress type and firmness

Once you have decided on the right size, it is worth thinking about how mattress type and firmness interact with that choice. Larger mattresses, especially in king and super king sizes, can be heavier and more difficult to rotate or move, particularly in hybrid and spring designs that use steel coils. Foam mattresses tend to be lighter and easier to manoeuvre, which may matter if you will be turning the mattress regularly or handling it alone.

Firmness also affects how spacious a mattress feels. A softer mattress allows you to sink in more, which some people find cocooning but others find restrictive, especially on narrower sizes. Medium or medium-firm mattresses often provide a good balance of contouring and freedom to move, which can be helpful if you are sharing a double or small double. For more guidance on comfort levels, the guide on how firm your mattress should be explains how different firmness ratings suit various sleeping positions.

Heat build-up can be another factor, especially on larger mattresses that hold more body heat. If you know you are a warm sleeper or live in a home where bedrooms tend to get stuffy, pairing your chosen size with a design that focuses on breathability can be very helpful. You can explore more focused advice in this guide to cooling mattresses and cooler sleep, and then apply those ideas to the size that best fits your room and lifestyle.

Conclusion

Choosing the right mattress size is as much about how you live as it is about how you sleep. When you match the size to your height, body shape, sleeping habits and bedroom space, everything from bedtime to morning routines becomes easier and more comfortable. Start by measuring your room and bed frame, then think about whether you sleep alone or share, whether you need extra length, and how much floor space you want to keep clear.

For children and teens, a thoughtfully chosen single or small double gives them room to grow without overwhelming the room. Supplementary options like an inflatable ready bed or a supportive kids’ spring mattress can address different stages and situations without complicating the main bedroom layout.

Once you are confident about size, you can focus on finding the best type, firmness and features for your needs, knowing that your chosen mattress will fit both your room and your routine. Combining the right dimensions with a suitable design gives you the best chance of consistently comfortable, restorative sleep.