Mirror Measuring Guide

How to Measure for Your Mirror

This guide explains how to measure a mirror accurately, including standard shapes and more complex made to measure designs. Accurate measuring is essential because all our mirrors are cut to order. Always measure in centimetres (cm) or millimetres (mm) for the best results.

General Measuring Rules: How to Measure a Mirror

  • Use a metal tape measure for accuracy.
  • If the mirror is to fit a whole wall or space measure the width and height in at least two or three places.
  • If the measurements differ slightly, always use the smallest.
  • For alcoves or recesses: If the mirror is to fit between two walls or inside a recess, allow a tolerance of 3mm on each side (6mm total) so the mirror can be manoeuvred safely into place.
  • When you measure for a mirror, always double check your dimensions before ordering.

How to Measure Irregular or Non Rectangular Shapes

If your mirror is not a simple square or rectangle, and the shape includes angles that are not 90 degrees, it is still easy to measure. We can cut mirrors to almost any straight edged shape as long as we have accurate measurements along with a diagram or a template to work from.

Shapes with Sloping Sides or Uneven Heights

For shapes where the left and right sides are different heights or where the top or bottom edge slopes:

  • Measure the width at the top and at the bottom.
  • Measure the height on the left side and on the right side.
  • Include a diagram/drawing of the piece with the measurements on all four sides.

Triangles, Trapeziums, Parallelograms and other four sided shapes

For any three and four sided shape that is not a rectangle:

  • Measure all sides individually.
  • If any edges are not perfectly straight (e.g. for an arched top), note this so we can discuss options.
  • If the mirror is to fit into a recess, remember to allow a 3mm tolerance on each side.
  • Include a diagram/drawing of the piece with the measurements on all sides.

Multi Sided Shapes (five or more sides)

  • Measure each side in order, working clockwise.
  • Note the length of every side and confirm whether each angle is roughly sharp, square or obtuse.
  • Provide a diagram/drawing of the piece with the measurements on all sides.
  • We may require a template.

When a Template is Needed

  • If your shape is very specific, curved at any point, or needs to fit an uneven or non symmetrical space, a physical template is required.
  • This can be made from stiff card or plywood.
  • Make sure the edges are clean and accurate.
  • Lable the template ‘front’ and ‘back’.
  • Also label the template with your name and telephone number.
  • We will cut your mirror to match the template exactly.

Helpful Tips

  • Our knowledgeable team are on hand to help. Sketch your shape on paper and label each side with its measurement. Photograph the space where the mirror will go and email us the image. When in doubt, choosing to send a template removes any risk of incorrect angles or uneven walls.
  • Always double check all measurements before ordering.
  • For general safety advice when handling glass, you can read official guidance on the HSE website.

As a guide, we recommend 6mm mirrors for most wall mounted situations, and 4mm mirrors for wardrobe doors or furniture where you need to keep weight lower.

Points to Bear in Mind When

Measuring Above a Vanity or Basin

  • Measure the full width of the vanity or basin.
  • Decide whether you want the mirror:
    • the same width,
    • slightly narrower, or
    • running wall to wall.
  • Measure from the top of the basin or splashback to either:
    • the underside of any light fitting, or
    • the desired top height of the mirror.
  • Leave a small gap above taps and below lights so the mirror does not clash with fittings.

Measuring for a Full-Length Mirror

  • Decide where you will stand to check your reflection and make sure there is space to step back.
  • Measure from the floor to the height you want the top of the mirror to reach.
  • Choose a width that suits the wall space and does not obstruct doors or furniture.
  • Check that doors can still open comfortably.

Measuring Between Walls, in Alcoves or Above Fireplaces

For Alcoves or tight spaces:

  • Measure the width at the top, middle and bottom.
  • Use the smallest measurement so the mirror fits easily.
  • Leave a few millimetres tolerance for manoeuvring.

For Fireplaces:

  • Measure the width of the mantelpiece.
  • Decide whether the mirror should be:
    • the same width,
    • slightly narrower, or
    • wider if the wall allows.
  • Measure from the mantel to the ceiling or the point where you want the top of the mirror to sit.

Measuring for Mirrored Wardrobe Doors or Furniture

  • Measure the full size of the door or panel that will take the mirror.
  • If the mirror will be surface mounted, check the position of handles, hinges or trims that might affect the size.
  • For sliding doors, ensure mirrors will align neatly when the doors are closed.
  • We recommend using 4mm mirrors for wardrobes and furniture to reduce unnecessary weight.

Ready to order?

You can order your made to measure mirror directly on our Instant Mirror Quote page.