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How to Cut a Glass Mirror

Are you having a difficult time finding the perfect size or shape mirror for a particular space in your home? Read this guide to learn how to cut a mirror to the size or shape you desire.

Oval mirror with wooden frame on table iStock

Perhaps you’re looking to repurpose an old mirror, or you’re having a difficult time finding the perfect size or shape for a particular space in your home.

Whatever your reason for needing a custom-sized mirror, it will be much less expensive to cut it yourself than to have it professionally done. All you need are the right materials.

Materials for cutting a mirror

The most important thing you’ll need, besides the mirror itself, is a glass-cutting tool. Glass cutters are small and inexpensive, typically costing less than $10. They feature a small rolling cutter at the tip for scoring the glass, a notched section for gripping stray glass pieces, and a balled tip for deepening the score mark.

If you want to cut a mirror without a glass cutter, it’s possible to use a carbide scribe (typically used for writing on metal) or a steel file instead. These won’t be as easy to use as the rolling cutter, and they might produce a more jagged edge, but they can be used in cases where the edges won’t show.

Other materials you’ll need are:

As for the mirror itself, you shouldn’t attempt to cut anything longer than two feet in length. A pane larger than that will be difficult to handle, and the lack of control may result in inadvertent cracks or breakage.

Steps for Cutting a Mirror

After you’ve assembled the materials, here’s how to cut a mirror.

Step 1: Prep the mirror and yourself

  • Find a flat work surface large enough to lay the entire mirror on and cover it with a soft material for absorbing pressure.
  • Lay the mirror on top of the soft surface, glass-side up, and use a glass cleaner to remove any dust or debris from its surface.
  • With a wax crayon, mark the length and width of the mirror size you want. Dab a few drops of mineral oil along these lines, and spread the oil with your fingers in a thin layer over them. The oil will keep the cutter cool as it scores the glass.
  • Put on safety goggles and gloves that have a rubber grip to protect yourself from the sharp edges of the cut glass.

Step 2: Score the mirror

  • Align a ruler along your marked line to provide a straight edge. The ruler length should exceed the mirror length.
  • Secure the ruler with a clamp, or just make sure you have a firm grip on it, as the mirror’s smooth surface can cause the ruler to slip.
  • Dab a drop of mineral oil on the tip of the rolling cutter and position it against the ruler, on the far end.
  • Applying a firm, controlled pressure, pull the cutter toward you; you want to cut into the glass with enough pressure to make a solid mark, but not break it with too much force. To avoid a jagged break, make the cut in a single direction—don’t backtrack or make multiple scores. You’ll hear a crackling sound as the mirror is scored.
  • After making your line, use the ball end of the glass cutter to gently tap the mirror, right next to the score mark, going up and down along the line. This further deepens the cut.

Step 3: Break the mirror along the scored line

  • Now it’s time to snap the mirror into two separate pieces. Position a wooden dowel (it should be longer than the mirror) beneath the mirror, directly under the length of the score mark.
  • With one hand holding one side of the mirror steady, use your other hand to firmly press down the other side.
  • The mirror should snap into two clean pieces. If any jagged pieces remain, use the notches of the glass cutter to remove them.
  • Alternatively, you can use the edge of a table instead of a wooden dowel. Carefully position the score line along the table edge, making sure the line juts out over the edge by a centimeter or so.
  • Then firmly snap the mirror into two pieces.

Step 4: Sand the mirror edge and clean up

  • Using 200-grit sandpaper, file the jagged edge of the mirror until it’s smooth and safe to handle.
  • Make sure to thoroughly clean the workspace, as there may be tiny shards and slivers of glass that are hard to see.
  • Go over the area with a vacuum and wet paper towel to ensure that you catch all the pieces.