Most people start with a rough idea of the size they want. Tall, wide, large enough to see properly but not so large it overpowers the wall. What tends to catch people out is the gap between that instinct and the measurements that actually work in the room.
Getting the size right is one of the most important decisions in the process, and it is easier to do well once you know what to measure.
Width: the number most people underestimate
Width tends to matter more than height in most bathrooms because it determines how the mirror relates to the basin or vanity unit beneath it.
A mirror that is the same width as the vanity looks balanced but can feel a little safe. Going slightly wider, by 100 to 150mm on each side, gives the wall a more considered, deliberate look. Going significantly wider than the vanity only works well if the mirror has somewhere to go, such as spanning the full width between two walls or aligning with another architectural feature.
The mirror should not extend beyond the walls on either side, and it should not run past any adjacent cabinets, shelving, or towel rails that would interrupt the view.
Height: what the existing posts have covered
The question of mounting height has its own set of considerations, and these are covered in detail in the guide on how bathroom mirror height affects comfort and clarity. The short version: most people find the centre of the mirror works best between 120 and 170cm from the floor, depending on the height of the people using it.
For the mirror's own height, the general principle is that a taller mirror creates a more open feeling and reflects more of the room. A shorter mirror can work well in compact spaces or where there is something directly above the mirror, such as a cabinet or low ceiling.
How to measure your wall space
The most reliable approach is to mark out the available space on the wall before ordering.
Measure from any fixed obstruction on one side (a cabinet edge, a wall, a pipe boxing) to any fixed obstruction on the other. That gives your maximum width. Then measure from the top of the basin or vanity to the ceiling, or to the bottom of any overhead cabinet. That gives your available height.
Within those maximums, leave at least 20mm clearance on each side and at the top. This prevents the mirror from butting up against fixtures and makes installation easier.
Once you have your available space, consider how much of it you want the mirror to fill. A mirror that takes up most of the available width will feel more impactful. A smaller mirror in the same space will feel more considered and easier to balance with other bathroom elements.
Small bathrooms and narrow walls
In compact bathrooms, the instinct is often to choose a smaller mirror to avoid the space feeling cramped. A taller, narrower mirror can actually work better than a wide, low one, as it draws the eye upward and makes the ceiling feel higher.
For narrow walls where width is constrained, a tall backlit mirror can be a good solution. The vertical proportion works well in tight spaces and the integrated lighting means the room does not need additional fixtures above or beside the mirror.
When standard sizes do not fit
Off-the-shelf mirrors come in fixed increments, which means the gap between a mirror that fits and a mirror that is slightly too wide or too short is often just a few centimetres. In a bathroom where the available space is an unusual dimension, or where the proportions need to match tiling or cabinetry precisely, a standard size will not always look right even if it technically fits.
A bespoke mirror is made to your exact measurements. It removes the compromise of adjusting your layout to fit a standard product. The bespoke mirror service walks through how to provide your measurements and what to specify when you order.
If you would like help choosing the right mirror for your space, the Light Mirrors team is happy to advise. Visit the full mirror range or get in touch directly to talk through your require.
