What are the standard vanity unit sizes in the UK?

Common UK vanity unit widths are 400mm (cloakroom), 500mm (compact), 600mm (standard single basin), 750-800mm (wider single), 900mm (generous single or narrow double), and 1200mm (double basin). Depths typically range from 400mm (cloakroom) to 500-600mm (standard). Heights are usually 800-850mm including the worktop, matching standard basin mounting height.

What depth vanity unit do I need for a cloakroom?

For a cloakroom, a 400mm deep vanity unit is usually sufficient and helps maximise floor space in a small room. Slimline units as narrow as 350mm depth are available but may require a compact bottle trap and careful plumbing. Standard 500mm depth units work well in cloakrooms that are at least 1.2m wide, giving more worktop space and storage.

How much clearance do I need for plumbing behind a vanity unit?

Allow at least 80mm behind the back panel for waste pipes (32mm) and hot/cold supply pipes (15mm). Most vanity units have a pre-cut or removable back panel to accommodate plumbing. If the waste pipe exits from the wall rather than the floor, ensure the unit back panel can be cut without compromising structural integrity. Push-fit connections are recommended for accessibility.

Can I fit a double basin in a 900mm unit?

A 900mm vanity unit can technically accommodate two small basins, but it is tight. Each basin typically needs at least 400mm width plus a 100-200mm gap between them. For comfortable use, a 1200mm or wider unit is recommended for double basins. Many UK manufacturers offer purpose-built double basin units in 1200mm and 1500mm widths.

Should I choose doors or drawers for my vanity unit?

Drawers offer better access and organisation for bathroom storage, as you can see all contents without bending down. However, drawers must be cut around waste pipes, which reduces usable depth in the top drawer. A popular configuration is two drawers below with a false drawer front at the top (behind the basin). Doors are simpler for plumbing access but less organised. Soft-close mechanisms are recommended for both.

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Vanity Unit Sizing Calculator — Basin, Clearance & Storage

Calculate vanity unit sizes with basin clearance, plumbing offsets and storage capacity.

Available Wall Width

Measure the wall space for the unit

Basin TypeHow the basin fits into/onto the unit

Number of BasinsSingle or double basin

Bathroom TypeAffects size recommendations

How We Calculate This

This calculator recommends the best vanity unit size based on your available wall space, basin type, bathroom type and plumbing requirements.

How it works

Width matching: Finds the largest standard UK unit size that fits your available wall space
Basin clearance: Ensures sufficient width for the selected basin type and count
Plumbing check: Verifies depth and offset clearances for waste and supply pipes
Storage volume: Calculates usable internal volume accounting for carcass thickness and plumbing zone
Configuration: Suggests door and drawer counts based on unit width and selected style

Standard UK vanity units range from 400mm cloakroom to 1500mm double basin units. Dimensions follow common UK manufacturer standards from suppliers like Roper Rhodes, Burlington, Britton and Hudson Reed.

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Verify with your supplier.