Comparing memory foam mattress sizes UK is easier when you use exact centimetre dimensions rather than relying only on names such as Double or King. Bed labels are useful, but older frames, imported furniture, caravans and handmade beds do not always match the size a buyer expects.
The current All Foam standard mattress range is available in Single, Double, King Size and Super King. The custom mattress builder uses the same four online sizes, with selectable depth and layer construction. Non standard widths, lengths and shapes need to be discussed with the All Foam team before ordering.
This guide explains the listed dimensions, how to measure a frame and what information is required for a custom foam cut.
All Foam standard mattress dimensions
The current All Foam dimensions are:
- Single: 90cm wide by 190cm long.
- Double: 135cm wide by 190cm long.
- King Size: 150cm wide by 198cm long.
- Super King: 180cm wide by 198cm long.
Use these exact figures when checking a bed. Do not assume that every UK retailer or every existing frame uses identical measurements. The name may be the same while the actual dimensions differ slightly.
The All Foam mattress page shows each available size and current price for Deep Sleeper Comfort, Deep Sleeper Back Care and Luxury Deep Sleeper.
Single mattress size
The All Foam Single measures 90cm by 190cm. It is intended for one sleeper and is commonly used in children's rooms, guest rooms and smaller bedrooms.
Measure the internal width of the frame at the head, middle and foot. Then measure the usable length from the inside of the head end to the inside of the foot end. Raised side rails, brackets and corner posts can reduce the available space.
Also check the depth of the mattress. A deeper mattress changes the height of the sleeping surface and can affect guard rails, headboards and fitted sheets.
Double mattress size
The All Foam Double measures 135cm by 190cm. It can be used by one person who wants more space or by two people where room size is limited.
A double frame should be checked for centre support. Many larger bed frames use a centre rail and support legs to prevent bowing. A missing or loose centre support can make the mattress dip even when the foam itself is sound.
Measure both sides and the centre. If the frame is not square, one end may be narrower. Use the smallest reliable internal measurement and contact All Foam if the difference is significant.
King Size mattress dimensions
The All Foam King Size measures 150cm by 198cm. The extra width gives two sleepers more personal space than a Double, and the longer length can suit taller users.
Do not order from the word King alone. Imported frames and some older furniture may use a different length. Measure the exact platform or internal frame and compare it with 150cm by 198cm.
Check access through the property as well. A foam mattress may be compressed for delivery, but the final product still needs enough room to lie flat and be positioned safely.
Super King mattress dimensions
The All Foam Super King measures 180cm by 198cm. It offers the widest standard sleeping area in the range.
The frame needs even support across the full width. Inspect centre rails, legs and slats carefully. A wide frame with poor central support can create movement or sagging that affects the mattress.
Measure the room as well as the frame. Allow space to walk around the bed, open drawers and move furniture. A mattress can fit the frame but make the bedroom impractical.
Why you should measure the frame, not the old mattress
An old mattress may have changed shape. Its cover can stretch, edges can compress and foam can become slightly rounded through use. Measuring it may repeat an error or hide a poor fit.
Measure the structure that will support the new mattress. For a framed bed, use the internal width and length. For a divan, measure the top surface. For a platform bed, check the full supported area and any raised lip around the edge.
Take each measurement at least twice. Record it in centimetres and note where it was taken. Do not round a figure simply because it is close to a familiar bed size.
The how to measure foam guide explains a reliable measuring process for rectangular and unusual spaces.
Allow for real manufacturing and frame variation
Mattresses and frames are physical products, not perfectly machined metal components. Small manufacturing tolerances can exist, and soft materials can compress when measured.
The National Bed Federation notes that there is no single legal mattress size tolerance in the UK and that accepted industry practice can allow variation around the stated dimensions. This is another reason to avoid ordering a mattress that is exactly the same as a very tight opening without discussing the fit.
A mattress that is too large can bow, curl at the edges or be difficult to rotate. A mattress that is much too small can move and leave uncomfortable gaps.
When a frame opening is unusually tight, provide the measurements to All Foam before ordering.
Mattress depth matters as much as width and length
All Foam standard mattresses have different finished depths:
- Deep Sleeper Comfort: 20cm.
- Deep Sleeper Back Care: 22.5cm.
- Luxury Deep Sleeper: 25cm including the cover.
Depth affects fitted sheet size, bed height and the visible amount of headboard. It can also affect safety on a bunk or raised bed because the distance between the mattress surface and a guard rail changes.
The memory foam mattress buying guide compares the layer construction behind these depths.
Check fitted sheets and mattress protectors
Bedding is sold by named size, but pocket depth varies. A fitted sheet can match the width and length while still being too shallow for the mattress.
Check the stated pocket depth and allow enough material to fit around the full mattress without pulling the corners upwards. A protector also needs to match the finished depth.
Do not compress the mattress with undersized bedding. Tight covers can affect the way the upper surface responds and may cause the sheet to come loose during use.
Standard sizes in the custom mattress builder
The custom foam mattress builder prices four standard UK sizes online:
- Single: 90cm by 190cm.
- Double: 135cm by 190cm.
- King Size: 150cm by 198cm.
- Super King: 180cm by 198cm.
You can choose a total depth of 8, 9 or 10 inches and select one, two or three foam layers. The builder controls the available layer splits so the base remains at least 6 inches and additional layers are at least 1 inch each.
The word custom refers to the selectable construction. It does not mean the online calculator accepts any width, length or shape.
When a custom foam cut is required
A non standard mattress may be needed for an antique bed, imported frame, caravan, motorhome, campervan, boat or handmade sleeping platform. Curved corners, tapered sides, wheel arch cut outs and split sections cannot be described by a standard width and length alone.
Contact All Foam before ordering and provide:
- Finished width and length.
- Required depth.
- A clear drawing with every dimension.
- Orientation, including head, foot, left and right.
- Details of curves, cut outs and angled sides.
- The intended use and bed base.
- Any access restrictions through doors, stairs or hatches.
A full size paper or card template may be requested for complicated shapes. Do not send only a photograph because perspective can distort dimensions.
Measuring an odd shaped mattress space
Start by drawing the shape from above. Mark a centre line and identify the head and foot. Measure the maximum length and width, then add the position and size of every curve or notch.
For a tapered bed, record widths at several points along the length. For a rounded corner, a template is usually more reliable than trying to describe the curve with one radius. For a wheel arch, record its distance from two fixed edges so the position cannot be reversed.
Mark which side faces upwards. A shape that appears symmetrical in a photograph may not be symmetrical in the actual vehicle or boat.
The custom mattress sizing guide for caravans, motorhomes and boats gives more detail on shaped sleeping areas.
Consider split mattresses
A large custom mattress may fit the sleeping platform but not pass through a narrow door, stairway or boat hatch. A split construction can make access easier.
Decide where a split could sit without creating an uncomfortable join. The split may need to follow an existing bed section, lifting panel or access hatch. Measure each part separately and show how the pieces meet.
Do not assume that a deeply compressed foam mattress will pass through every opening. Discuss access with All Foam before production.
Check the base and ventilation
The mattress needs a level and evenly supportive surface. Gaps, broken slats and unsupported sections can change how the foam feels and wears.
Compact spaces need ventilation. Condensation can form beneath a mattress on a cold platform, especially in boats and leisure vehicles. Keep fixed vents clear and allow the mattress and base to air. Do not block safety ventilation in a caravan, motorhome or boat.
The base design, material and airflow should be considered before the foam is ordered, not after damp appears.
Common mattress size mistakes
Ordering from the old product label is a common mistake. Always measure the frame.
Rounding 198cm up to 200cm or assuming every King is identical can cause a poor fit. Use the exact dimensions shown by the supplier.
Ignoring depth can lead to unsuitable bedding or a sleeping surface that is too high for the furniture.
For custom shapes, failing to mark orientation can create a mirror image. Missing access restrictions can leave a mattress that cannot be moved into position.
Finally, do not subtract an arbitrary amount from every measurement. Foam fit depends on the shape, cover and application. Ask All Foam what allowance is appropriate.
A final measuring checklist
Before ordering, confirm:
- Internal frame width at the head, middle and foot.
- Internal length on both sides and through the centre.
- Finished mattress depth.
- Bed base condition and support.
- Fitted sheet and protector depth.
- Room and property access.
- Orientation and templates for non standard shapes.
- Any split sections or lifting panels.
- Ventilation beneath the mattress.
Final answer
The names Single, Double, King and Super King are only the starting point. The exact All Foam dimensions are 90cm by 190cm, 135cm by 190cm, 150cm by 198cm and 180cm by 198cm.
Measure the bed frame, check mattress depth and inspect the base before ordering. Use the online builder when one of the four standard sizes suits the bed and you want to choose the internal foam construction. Contact All Foam for a non standard width, length or shape, and provide a detailed drawing or template rather than a guess.