Bathroom Spacing Calculator — Minimum Clearances & Layout

BS 6465-2 recommends an activity space of about 600mm deep in front of a WC pan (the standard used here), plus at least 200mm clear EACH SIDE OF THE PAN EDGE for use and cleaning. For a Part M M4(1) visitable WC, Approved Document M Vol 1 requires 750mm in front of the pan and, for head-on access, at least 450mm EITHER SIDE of the WC centre line (500mm preferred) — measured from the centre line, not clear of each edge. The opposite side may be reduced to 400mm only where access to the WC is oblique.

Part M of the Building Regulations (Access to and use of buildings) sets minimum accessibility standards. For dwellings, Part M Category 1 (M4(1) visitable) requires a WC with 750mm frontal clearance and, for head-on access, at least 450mm either side of the WC centre line (500mm preferred); only where access is oblique may the side opposite the approach reduce to 400mm. Categories M4(2) (accessible/adaptable) and M4(3) (wheelchair user) add larger zones and, for the wheelchair standard, a 1500mm turning space — this calculator models the M4(1) WC zone only, not the full M4(2)/M4(3) turning circle.

There is no absolute minimum bathroom size in UK Building Regulations, and BS 6465-2 deliberately gives appliance space recommendations rather than fixed room sizes to keep design flexible. As a real-world rule of thumb, a small en-suite with WC, basin and shower typically needs at least 1.2m x 1.7m (about 2 m²), and a standard family bathroom with bath at least 1.7m x 2.4m (about 4 m²) — figures that assume adjacent fixtures SHARE their activity spaces. This calculator's pass/fail test is intentionally more conservative: it SUMS each fixture's footprint plus clearance without sharing overlap, so a real ~4 m² family bathroom can still report FAILS here yet lay out perfectly well on a scaled drawing. Treat a FAILS as a prompt to plan the layout, not a verdict that the room is too small. These figures assume standard clearances, not Part M.

Building Regulations do not mandate door swing direction for standard bathrooms, but an outward-opening door saves space inside the room and is safer in an emergency (you can access someone who has collapsed). However, outward-opening doors require hallway clearance. Sliding or bi-fold doors are a good compromise for small bathrooms.

Allow roughly 200-250mm minimum between a WC and an adjacent basin (measured edge to edge, not centre lines), with 250-300mm preferred. BS 6465-2 ties the gap to cleaning and bin access (around 210mm), so a little over 200mm is the practical floor. For Part M layouts allow at least 300mm. To facilitate cleaning, BS 6465-2 also recommends a gap of at least 65mm between adjacent appliances.