If the room is a simple rectangle or square:

• Measure the length
• Measure the width
• Multiply them together

So, a room 5m long and 4m wide = 20sqm. Easy.

If the room is shaped differently (like an L or has a nook), just break it into smaller rectangles, measure those and add them all up.

Walls are basically the same formula.

• Measure the height (or the height to where you want to tile to)
• Measure the width
• Multiply them together

If you’ve got more than one wall, do them one by one and then add them together.

Tip: Don’t forget to take out windows and doors. Example:

• Wall = 2.5m high × 3m wide = 7.5sqm
• Window = 1m × 1.5m = 1.5sqm
  So you only need to tile 6sqm.

Tiles aren’t like paint, you can’t use up every last bit. You’ll cut some, break some, and sometimes need extra to match a pattern. The safe bet is to add 15% more. If you’re laying something tricky like herringbone, bump that up to 20%.

Example: Room is 20sqm. Add 15% → 20 × 1.15 = 23sqm needed.

Keep the maths separate. Floor tiles in one column, wall tiles in another. Add 15% on each. That way you won’t accidentally short one style and over-order another.

• Floor = 20sqm
• Walls to 1m high = 17.1sqm (after subtracting door etc)
• So floor tile total = 37.1sqm → with wastage = 42.7sqm
• Upper walls = 22.8sqm (after subtracting window etc)
• With wastage = 26.2sqm

And remember: tiles are sold in boxes, so round up to the nearest box.