Small Double Waterproof Mattress Protector

UK beds come in five standard sizes: Single (90 × 190cm), Small Double (120 × 190cm), Double (135 × 190cm), King (150 × 200cm) and Super King (180 × 200cm). Every duvet, sheet, topper and protector we sell is sized to match these — confirm your bed size in the table below, then jump to the guide for the product you're buying.

Watch out for cross-market confusion: a UK King (150 × 200cm) is closer to a US Queen than a US King, and IKEA/European beds run to different sizes (a Euro double is 140 × 200cm — wider and longer than the UK 135 × 190cm standard), so always measure the mattress in centimetres before ordering.

UK bed size chart (mattress, duvet and sheet sizes)

*Some suppliers cut single duvets at 140 × 200cm — check the label. UK sizes follow National Bed Federation standard tolerances. Measure your mattress, not your bed frame — frames add several centimetres and cause most wrong-size orders.

Why mattress depth matters as much as width

Standard fitted sheets are 25–30cm deep; modern pillow-top and hybrid mattresses reach 30–40cm, and a topper adds more. Our extra deep fitted sheets have a 40cm fit. Measure mattress + topper together; if the total is over 30cm, standard sheets will keep popping off.

Find the guide for your product

• Duvet sizes — match duvet dimensions to your bed, and see the duvet tog guide for the right warmth.
• Pillow size guide — standard, V shape, U shape and bolster sizes explained.
• Pillowcase sizes — getting the right fit over your pillows.
• Fitted sheet sizes — sizes plus the depth you need for deep mattresses.
• Cushion insert size guide — picking insert sizes for a plump, full look.

Choosing, not just measuring

Once the size is settled, these guides cover the rest: how to choose a pillow, the pillow firmness guide, the pillow filling guide and how to choose a duvet. For upkeep, see how to wash pillows and how to wash a duvet.

Quick answers

What size is a UK King duvet?

225 × 220cm — it fits a 150 × 200cm King mattress with overhang on both sides.

Should a cushion insert be bigger than its cover?

Yes, one size (about 5cm/2") bigger gives a plump look; same-size inserts sag at the corners.

Why won't my fitted sheet stay on?

Depth — if mattress plus topper exceeds the sheet's pocket depth, the corners pull off; measure both together.

Do Small Double and Double beds take the same duvet?

Yes, both use 200 × 200cm.

What size are UK pillows?

Standard UK pillows are 74 × 48cm. The pillowcases and protectors that go over them are cut slightly larger at 50 × 75cm so they don't compress the filling. Square/Euro pillows are 65 × 65cm.

Written by the Posh Tag team, Rochdale, Lancashire. Published: 12 July 2026. Last reviewed: 14 September 2026. Questions? Call +44 7414 441213.