Start with a bathroom mirror the same width as your vanity or slightly narrower, then adjust for wall space, lighting and the reflection you need. This is a styling starting point, not a fixed rule. There is no general requirement for a mirror to be 1.5 times wider than the cabinet or as tall as the person using it.
The right size feels balanced and works comfortably every morning. Measure first, then use a full-size outline on the wall to compare shapes before ordering. A circle, arch and rectangle can use the same wall space very differently.
Measure these four things
- The width of the vanity or basin arrangement you want the mirror to relate to.
- The usable wall width between lights, cabinets, screens and other obstructions.
- The available height above taps and below the ceiling or fittings.
- The reflection each regular user needs from their normal position at the basin.
Include frames, brackets and the clearance needed for fitting. A decorative rope or tall crest can add height beyond the glass itself. For example, the round mirror with a rope detail should be considered as a complete outline, not only a circular diameter.
Three real sizes to tape out
40 × 50 cm frontlit LED mirror — £89. A compact format for a small wall area. Mark 40 cm wide and 50 cm high, then check that the reflection remains useful for everyone using the basin. Adjustable lighting and anti-fog add everyday convenience.
Browse small bathroom mirrors when fittings limit the available wall. A smaller room does not always demand a tiny mirror: the actual clear wall and viewing position matter more than the room label.
60 cm round frontlit and backlit mirror — £128. A circle softens straight cabinetry and needs 60 cm of height as well as width. Its corners do not provide reflection as a rectangle would, so check the outline at the planned height rather than comparing width alone.
140 × 70 cm dual-light bathroom mirror — £299. A wide format for a generous vanity or two basins, with front and back lighting, dimming and anti-fog. It offers a continuous reflection instead of two separate focal points. Check the supporting wall and fitting route as well as the dimensions.
Prices and the linked in-stock options were checked on 27 October 2026. Any checkout promotion is applied separately.
One wide mirror or two above a double vanity?
A single mirror connects the two basin areas visually and can make the wall feel calmer. Two mirrors create separate personal spaces and leave a gap for a wall light or architectural feature. Align each choice with the basin positions, not just the outer cabinet edges.
For a shared bathroom, check both people’s reflections and control reach. Our large bathroom mirror collection gives you wider formats to compare, while the vanity mirror guide explains the role of the reflection at the basin.
Choose height for the users, not a standard floor measurement
Place the proposed outline so shorter and taller users can see comfortably. Leave practical clearance above taps and make sure a tall mirror does not crowd the ceiling or block another fitting. The centre of a decorative mirror is not always the best reference point for a shared bathroom.
Use our mirror size calculator for a starting size, then confirm it on the real wall. If you are between two options, tape out both and compare them from the doorway as well as from the basin.
Finish with the style you enjoy
Once the dimensions work, choose the lighting and frame that complete the room. See statement mirror ideas, bathroom mirror styles and our online wall-mirror buying guide for the next stage. The best size is the one that looks considered and gives you the reflection you need.
Enjoy free UK delivery, a 3-year warranty and free replacement if your mirror arrives damaged.