What are the UK standard mattress sizes?

UK standard sizes are: Single 90x190cm, Small Double 120x190cm, Double 135x190cm, King 150x200cm, Super King 180x200cm. Note that UK sizes differ from EU and US sizes. Always measure your actual mattress before building.

What spacing should bed slats have?

Most UK mattress warranties require slat gaps of no more than 70mm (some specify 60mm). For memory foam mattresses, closer spacing (30-50mm) is recommended for better support. This calculator automatically determines the number of slats to keep gaps within 70mm.

Do I need a centre rail on a bed frame?

A centre support rail is strongly recommended for any bed wider than 1400mm (king size and above). It prevents slats from bowing under body weight and significantly increases the rigidity of the frame. Double beds (1350mm) can manage without but benefit from one.

What timber should I use for a bed frame?

Side rails and head/foot boards should be hardwood (oak, ash, beech) or quality softwood (redwood pine) at least 22mm thick and 150-200mm wide. Slats can be thinner (18mm) but should be at least 70mm wide. Use straight-grained stock without large knots for rails.

How much clearance should I allow around the mattress?

Allow 10mm clearance on each side and each end between the mattress and the frame interior. This makes it easy to fit sheets and prevents the mattress from being squeezed, which can damage it and void the warranty.

WoodCalcs

Bed Frame Calculator — Dimensions & Slat Spacing

Calculate bed frame dimensions, slat spacing, and timber quantities for UK standard mattress sizes.

Mattress Size

Side Rail Height

Side Rail Thickness

Slat Thickness

Slat Width

Timber Price per Metre (optional)

How We Calculate This

This calculator sizes a bed frame around UK standard mattress dimensions with proper clearances and slat spacing.

Frame sizing

Internal dimensions = Mattress size + 20mm (10mm clearance each side)

External dimensions = Internal + (2 x rail thickness)

Slat calculation

Number of slats = ceil(Frame length / (Slat thickness + Max gap))

The maximum gap is 70mm per UK mattress warranty requirements. Actual spacing is then calculated from the number of slats to distribute them evenly. Beds wider than 1400mm automatically include a centre support rail with two half-width slats per position.

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates. Always verify measurements and material quantities before cutting or purchasing.