Tile Calculator
Calculate how many tiles a floor or wall needs, including grout joints and a cutting allowance.
Formula
Each tile occupies its own size plus one grout joint in each direction. Divide the area by that, then add a cutting allowance.
- Area per tile (m²) = (Tile length + joint) × (Tile width + joint)
- Tiles = Area ÷ Area per tile × (1 + allowance % ÷ 100)
- Boxes = ceiling( Tiles ÷ Tiles per box )
Worked example
20 m² of floor in 600 × 600 mm tiles with 3 mm joints, 4 tiles per box, 10% allowance.
- Area per tile = 0.603 × 0.603 = 0.3636 m²
- Tiles per m² = 2.75
- Net tiles = 20 × 2.75 = 55
- With 10% allowance = 60.5, so 61 tiles
- Boxes = 61 ÷ 4 = 15.25, so 16 boxes
61 tiles, which means buying 16 boxes and having 3 spare.
Assumptions and limitations
- Tiles are laid in a straight grid. Diagonal, herringbone and offset patterns generate substantially more cutting waste.
- The grout joint is added once per tile in each direction, which is the standard coverage convention.
- No allowance is made for tiles lost to a badly out-of-square room beyond the general cutting allowance.
- Boxes are assumed to contain the stated number of tiles. Some suppliers sell by square metre per box instead.
What this calculator does not do
- Does not calculate adhesive, grout, primer or levelling compound. Those follow the manufacturer's coverage rates for the trowel and joint size used.
- Does not plan the setting out. Where the cuts fall, and whether the layout starts from a centre line or a wall, changes the real cutting waste.
- Does not cover trims, skirting tiles, movement joints or thresholds.
Practical tips
- Increase the allowance to 15–20% for diagonal layouts and patterned tiles. The offcuts from a diagonal layout are rarely reusable.
- Order all tiles for a room in one go and check the batch numbers match. Shade variation between batches is common and very visible.
- Keep at least a few spare tiles after the job. Discontinued lines are a real problem when one tile cracks two years later.
Frequently asked questions
How many tiles do I need per square metre?
Divide one square metre by the tile size plus grout joints. For 600 × 600 mm tiles with 3 mm joints, that is about 2.75 tiles per square metre.
How much extra should I order for cutting?
Around 10% for a straight layout in a simple rectangular room. Push it to 15–20% for diagonal patterns, small rooms with many cuts, or tiles with a directional pattern.
Do grout joints really matter to the count?
On small tiles, considerably. With 100 mm mosaics and 3 mm joints the joints add about 6% to the effective tile size, which is enough to change the order.
Should I buy whole boxes?
You will have to — most suppliers sell full boxes only. The calculator shows how many spare tiles the rounding leaves you, which is worth keeping for repairs.
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Estimating tool, not a design. This calculator works out quantities from the dimensions you enter. It does not size any structural member, verify a design, or confirm compliance with any building code. Check every result against your project specification and applicable local standards, and involve a qualified engineer where the work requires one.