Double Mattress vs King Size Mattress: Which Size is Right for You?
Posted by Tom Hughes on
Most couples buying a new mattress underestimate how much size affects sleep quality. A double mattress gives each person just 67.5cm (26.5 inches) of personal sleeping width, significantly less space than most people realise. If you are shopping for mattresses in Flintshire and wondering whether to go double or king, this guide gives you a straight answer based on bedroom dimensions, sleeping habits, and what we see working for real families in North Wales and the Wirral every single week.
Table of Contents
Quick Takeaways
|
Key Insight |
Explanation |
|---|---|
|
A double mattress is 135cm wide x 190cm long |
That gives two adults just 67.5cm each, narrower than most single mattresses sold today |
|
A king size mattress is 150cm wide x 200cm long |
The extra 15cm in width and 10cm in length makes a measurable difference for couples and taller sleepers |
|
Your bedroom needs at least 60cm clearance on each side of the bed |
A king size bed frame requires a room at least 3.5m x 3.5m to feel comfortable and safely accessible |
|
Doubles suit solo sleepers and guest bedrooms well |
For single adults who want room to move, or for a spare room used occasionally, a double is efficient and cost-effective |
|
Couples sleeping with a pet or a restless partner benefit most from king size |
The wider sleeping surface reduces motion transfer disturbance and gives both partners genuine personal space |
|
Mattress firmness matters as much as size |
Choosing the wrong tension on a king size mattress is just as disruptive to sleep as choosing the wrong size on a double |
|
Trying before buying is non-negotiable |
Online size guides help, but lying on both sizes in a showroom for at least 10 minutes each is the only reliable test |
Standard Sizes Explained: What Double and King Actually Mean
In the UK, a double mattress measures 135cm wide by 190cm long. A king size mattress measures 150cm wide by 200cm long. Those numbers sound modest on paper, but the difference in usable sleeping area is significant. A king size gives you 4,350 square centimetres more sleeping surface than a double.
There is also a super king size option at 180cm wide by 200cm long, which is a significant step up again. For context, the super king is essentially two single mattresses placed side by side. Most families in Connah's Quay and across the Wirral find that king size hits the sweet spot between practicality and comfort without demanding a bedroom the size of a hotel suite.
One common mistake is confusing a UK king size with a US king size. American king mattresses are 193cm wide, considerably bigger than what UK bedrooms are built to accommodate. When you are shopping at a local mattress showroom in Flintshire, every measurement will be in UK standard dimensions, so you will not run into that confusion.
Bedroom Space Requirements You Cannot Ignore
A double bed frame typically sits at around 145cm wide once the frame itself is included. Add 60cm clearance on each side for safe access and comfortable movement, and you need a room at least 2.65 metres wide just for the bed, not counting wardrobes or drawers. A king size bed frame runs to approximately 160cm wide, pushing that minimum room width to 2.8 metres.
In practice, most standard UK double bedrooms measure between 3.0 and 3.5 metres wide. That means a king size genuinely fits in most main bedrooms in North Wales and Cheshire without requiring any compromises. Smaller second bedrooms, typically around 2.5 to 2.8 metres wide, are better served by a double.
Measuring Your Bedroom Correctly
Measure wall to wall at floor level, not at cornice height. Bay windows, chimney breasts, and fitted wardrobe doors that swing outward all reduce the usable floor space. Mark the intended bed position with masking tape on the floor before visiting any showroom. This takes three minutes and saves enormous disappointment after delivery.
Pro tip: Measure the width of your staircase, landing turn, and bedroom doorway before ordering. A king size mattress is manageable in most UK homes, but very narrow Victorian terraces in Flintshire and Cheshire occasionally make delivery of larger mattress sizes genuinely difficult without specialist handling.
Who Should Choose a Double Mattress
A double mattress is the right choice in specific, clear-cut situations. It is not a compromise for everyone, but it is wrong for some buyers who choose it purely on price without thinking through their actual sleeping needs.
Solo Sleepers Who Want More Space Than a Single
Single adults who move around during sleep and find a single bed too restrictive will benefit from a double. It provides enough width for a comfortable night without taking over a modest-sized bedroom. Guest bedrooms that are used a few nights a month are another strong case for a double rather than a king.
Couples in Smaller Bedrooms
If your bedroom is genuinely under 3 metres wide, a double is often the only sensible option. A king size crammed into a room with inadequate clearance feels worse than a double with breathing room around it. Comfort is not just about the mattress surface. The whole room environment contributes to how restful the space feels.
Couples who are lighter sleepers and rarely disturb each other also get on fine with a double. Not every partnership needs the full width of a king. The key question is whether you regularly wake your partner up, or they wake you, through movement during the night.
Who Should Choose a King Size Mattress
For most couples sharing a bed as their primary sleeping arrangement, a king size mattress is the better long-term investment. The data consistently shows that sleep quality is one of the strongest predictors of daily mood, productivity, and physical health. Disrupted sleep from a cramped mattress is not a trivial inconvenience.
Taller Sleepers
Anyone over 6 feet tall will immediately notice the 10cm extra length a king size offers over a double. Sleeping with your feet pressing against the footboard, or hanging off the end, is uncomfortable enough to wake a heavy sleeper. If you or your partner are above average height, the king size is not a luxury. It is appropriate sizing.
Couples Who Share With Children or Pets
Families in North Wales know that weekend mornings often involve a small child climbing into the parental bed. A double mattress with two adults and a visiting child leaves no comfortable space for anyone. A king size handles this with significantly less disruption. The same applies to families with a dog that sleeps on the bed. It is a common reality in most households, and a king size accommodates it without resentment.
Pro tip: If you and your partner have significantly different preferred firmness levels, ask about zip-and-link king size mattresses when you visit our showroom. These split down the centre so each person sleeps on a tension suited to their body weight and sleeping position, without compromising on the shared sleeping surface. Or our Harrison Spinks range, all Harrison mattresses are available with split tensions on their left and right sides.
Mattress Cost
While king size mattresses typically cost 10-25% more than their double equivalents, many couples consider the extra sleeping space one of the best-value bedroom upgrades they can make. When spread across the lifespan of a quality mattress, the difference often works out to only a few pence per night.
Double vs King vs Super King: Side-by-Side Comparison
Understanding exactly where each size sits helps you make a definitive decision rather than guessing. Use this table as a reference point when discussing options with our team at the showroom in Connah's Quay.
|
Feature |
Double Mattress (135 x 190cm) |
King Size Mattress (150 x 200cm) |
Super King Mattress (180 x 200cm) |
|---|---|---|---|
|
Width per person (two adults) |
67.5cm |
75cm |
90cm |
|
Minimum recommended room width |
2.8m |
3.2m |
3.8m |
|
Best suited to |
Solo adults, guest rooms, smaller bedrooms |
Couples, taller sleepers, main bedrooms |
Couples wanting maximum space, large bedrooms |
|
Typical price range (UK) |
Lower |
Mid to higher |
Higher |
|
Bedding availability |
Widely available everywhere |
Widely available, good range |
Good range but fewer budget options |
|
Motion transfer impact for couples |
Higher, both partners can feel movement |
Reduced, especially with pocket sprung |
Lowest, ample space between sleepers |
Mattress Types That Work Best at Each Size
Size is only part of the decision. The internal construction of the mattress determines how well it actually supports your body and manages shared movement. This is an area where in-person advice from people who know the products makes a real difference.
Pocket Sprung Mattresses
Pocket sprung mattresses use individually wrapped springs that move independently. This means one person turning over does not send a wave of movement across the entire surface to disturb their partner. For couples on a king size, pocket sprung is almost always the right recommendation. The more springs per square metre, generally the better the contouring and support.
Memory Foam and Hybrid Options
Memory foam excels at pressure relief, particularly for side sleepers and people with hip or shoulder discomfort. On a double mattress, a memory foam option can feel warmer and more enveloping, which some solo sleepers love. On a king size shared by two people, a hybrid combining pocket springs with a memory foam comfort layer tends to give the best of both worlds: independent support plus pressure relief.
Considerations for Mobility Needs
Older adults or those with mobility challenges often find that a firmer mattress at the right height makes getting in and out of bed significantly easier. At Coast Road Furniture, this is something our team addresses directly. The combination of bed frame height and mattress thickness affects access just as much as it affects sleeping comfort. A king size at the right height with appropriate firmness can be transformative for someone who struggles with a low, soft double.
Visiting a Mattress Showroom in Flintshire
No amount of reading replaces lying on a mattress in person. This is not a cliché, it is a physical reality. Your body weight, sleeping position, and comfort preferences are unique to you. Two people of similar build can have completely opposite reactions to the same mattress.
Coast Road Furniture's four-floor showroom in Connah's Quay carries a wide range of beds and mattresses across both double and king sizes. Being a family-run business established since 1972, the team understands that local families in North Wales, Cheshire, and the Wirral are making significant purchases that need to last. There is no pressure to buy on the day, and the advice is genuinely tailored to your bedroom dimensions and sleeping needs.
We are open seven days a week, and free local delivery with professional setup is included. That means your new mattress arrives already positioned correctly, with all packaging taken away. Unlike ordering online and wrestling a vacuum-rolled mattress up a narrow staircase yourself, this is a complete service from selection through to setup.
If you are considering the transition from a double to a king size, bring your bedroom measurements and let the team at the showroom walk you through options that fit your space and budget. The difference a correctly sized, well-constructed mattress makes to sleep quality is one of the most consistent pieces of feedback we hear from customers after delivery.
Frequently Asked Questions
What is the difference in size between a double and a king size mattress in the UK?
A UK double mattress measures 135cm wide by 190cm long. A UK king size mattress measures 150cm wide by 200cm long. That is 15cm more width and 10cm more length on the king, giving a noticeably larger sleeping surface overall.
Is a king size mattress worth it for a couple?
For most couples sharing a bed every night, yes, a king size is worth the investment. A double gives each person only 67.5cm of sleeping width, which is less than a standard single mattress. The king size brings that up to 75cm each, reducing disturbance from movement and giving both partners enough space to sleep comfortably without compromising each other's rest.
What room size do I need for a king size bed?
A king size bed with frame typically measures around 160cm wide and 215cm long including a headboard. To allow 60cm clearance on each side and at the foot of the bed, your bedroom should ideally be at least 3.2 metres wide and 3.5 metres long. Measuring your specific room before visiting a showroom is always advisable.
Can I try double and king size mattresses before buying in Flintshire?
Yes. Coast Road Furniture's showroom in Connah's Quay stocks both double and king size mattresses across multiple brands and constructions. You can lie on each size and discuss your requirements with the team in person. This is the most reliable way to make a decision that suits your body and your bedroom, far more reliable than choosing from a size guide alone.
Does mattress firmness change between a double and king size version of the same model?
The firmness level, whether soft, medium, or firm, is consistent across sizes within the same mattress model. However, your body weight is distributed over a larger or smaller surface depending on the size, which can subtly affect how the mattress feels. Heavier sleepers sometimes find a king size feels marginally different from a double in the same model, which is another reason to try before committing.
What is a zip-and-link mattress and is it available in king size?
A zip-and-link mattress is a king or super king size mattress made from two separate halves that fasten together down the middle with a zip. Each half can have a different firmness level, making it ideal for couples with different comfort preferences. This option is available in king size and is worth asking about specifically when visiting the showroom if you and your partner prefer different tensions.