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Bathroom Electrical Zone Calculator — BS 7671 Zone Distances
Determine which electrical zone a proposed fitting falls in based on its distance from a bath or shower. Includes IP rating requirements, voltage limits and supplementary bonding guidance per BS 7671.
Length of bath or shower tray
Width of bath or shower tray
Top of bath rim or shower tray (0 for flush tray)
Floor to ceiling
For a tray-less shower / wet room (rim height 0), this makes Zone 1 a 1.2m radius from the fixed water outlet
Proposed Fitting Location
From the bath/tray edge; for a tray-less shower, from the fixed water outlet. Use 0 for directly above the fixture.
Height of the proposed fitting
BS 7671 standard: 2250mm
BS 7671 standard: 600mm
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How We Calculate This
This calculator determines which electrical zone a proposed fitting or outlet falls in, based on its distance from the bath or shower per BS 7671 Section 701.
Zone definitions
Zone 0: Inside the bath tub or shower tray basin.
Zone 1: The space directly above the bath or tray (the footprint), from the top of Zone 0 up to 2250mm from the floor (or to the ceiling if lower, or to the top of a fixed water outlet if higher).
Zone 2: Extends 600mm horizontally from the edge of the bath/tray (i.e. 0.6m beyond Zone 1), to the same height limit. Beyond 600mm there is no zone. For a shower with no tray (wet room) and a fixed head, Zone 1 is instead a 1.2m radius around the fixed water outlet and there is no Zone 2— beyond the 1.2m radius is outside all zones (BS 7671 reg 701.32.3).
A wash basin, its taps and a WC do notcreate any zone under BS 7671 Section 701 — only a bath or shower does.
IP rating & voltage
- Zone 0: IPX7 — SELV max 12V AC / 30V DC
- Zone 1: IPX4 (IPX5 with jets) — SELV 25V AC / 60V DC or suitable fixed equipment; no socket outlets
- Zone 2: IPX4 — fixed equipment + shaver supply unit (BS EN 61558-2-5)
- Outside zones: No minimum IP, but all circuits in the room must be 30mA RCD protected
All requirements per BS 7671:2018+A2:2022 (IET Wiring Regulations 18th Edition).
Frequently Asked Questions
BS 7671 (18th Edition) defines three zones in rooms containing a bath or shower. Zone 0 is inside the bath or shower tray. Zone 1 extends from the top of the bath/tray up to 2.25m height and directly above the bath/shower. Zone 2 extends 0.6m horizontally beyond Zone 1 at the same height. Each zone has different IP rating and voltage requirements for electrical equipment.
In Zone 0: IPX7 (can withstand immersion). In Zone 1: IPX4 minimum (splash-proof), or IPX5 if water jets are present. In Zone 2: IPX4 minimum. Outside all zones: no special IP rating is required, but IPX4 is still recommended in a bathroom environment. Always use equipment specifically rated for bathroom use.
Standard 13A socket outlets are not permitted in Zones 0, 1 or 2. They can only be installed outside all zones (more than 0.6m beyond Zone 2). The exception is a shaver supply unit conforming to BS EN 61558-2-5, which can be installed in Zone 2. All socket circuits must be protected by a 30mA RCD. Many bathrooms in the UK do not have any socket outlets.
Under the 18th Edition (Amendment 2), supplementary equipotential bonding is not required if the installation meets automatic disconnection times and all circuits are RCD-protected at 30mA. However, if there is any doubt about the installation meeting these conditions, supplementary bonding should be installed connecting all exposed and extraneous conductive parts (pipes, radiators, bath, towel rail) to the earth terminal.
Yes. Any new electrical circuit in a bathroom (a special location under BS 7671) is notifiable under Part P of the Building Regulations. This means you must either use a registered competent person (e.g. NICEIC, NAPIT, ELECSA) or submit a building notice to your local authority. Like-for-like replacements (e.g. swapping a light fitting in the same location and zone) are generally non-notifiable.
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Last updated: March 2026
Verified against UK standards · estimates only, confirm with your supplier.