Tile calculator: how many tiles do I need?

How many tiles do I need?

Divide the area to tile by the area of one tile plus one joint, add an allowance for cuts and breakage, and round up. Then divide by the tiles in a box and round up again.

Area per tile  = (tile length + joint) × (tile width + joint)
Tiles          = area to tile ÷ area per tile × (1 + waste %), rounded up
Boxes          = tiles ÷ tiles per box, rounded up

1. Choose Floor or Wall and enter each area's length and width (or height). Add more areas for an L-shaped room or several walls.
2. Pick a tile size or type your own, and the joint (grout line) width.
3. Choose the layout; it sets the waste allowance, which you can change.
4. Open Boxes and enter what the box label says, in tiles or in area, to get the boxes to buy.
5. Open Grout and adhesive for the tile thickness, grout bag size and trowel.

Worked example: a 4 × 3 m floor in 600 × 600 mm tiles

12 m² ÷ (0.603 × 0.603 m) = 33 tiles; with 10% for cuts, order 37. Grout for 3 mm joints in 10 mm tiles is 1.92 kg, and adhesive with a 10 mm notch trowel 54 kg, 3 bags of 20 kg.

1. Area: 4 × 3 = 12 m².
2. Area per tile with joint: (0.6 + 0.003) × (0.6 + 0.003) = 0.3636 m².
3. Tiles: 12 ÷ 0.3636 = 33; × 1.10 = 36.3, so order 37. In boxes of 4, that is 10 boxes.
4. Grout: (600 + 600) ÷ (600 × 600) × 10 × 3 × 1.6 = 0.16 kg/m² × 12 m² = 1.92 kg.
5. Adhesive: 12 m² × 4.5 kg/m² = 54 kg.

How many tiles for 10 m² or 100 sq ft

Tiles are sold in whole boxes, and box contents vary by maker and size, so check the label.

How much extra tile to allow for cuts

Allow about 10% extra for a straight layout, 15% for diagonal and 20% for herringbone. These are rules of thumb repeated by tile retailers and calculator sites; we found no standard that sets them.

Diagonal and herringbone layouts cut a tile at every edge, and small rooms, many corners and large tiles waste more. Keep a few spare tiles from the same batch for repairs, as shade can vary between batches.

How much grout do I need?

Grout per m² = (A + B) ÷ (A × B) × C × D × 1.6, with tile length A, width B, tile thickness C and joint width D in mm. Multiply by the area to get kilograms.

This is the formula MAPEI publishes in its Ultracolor Plus data sheet, where 1.6 is the density factor for that cement-based grout. As a check, a 300 × 300 × 10 mm tile with 3 mm joints gives 0.32 kg/m²; MAPEI's own table shows 0.3. Smaller tiles and wider joints use much more grout, because there is more joint per square metre. Epoxy and other grouts have different densities, so use the figure in their data sheet.

How much tile adhesive do I need?

About 3 kg per m² with a 6 mm notched trowel and 4.5 kg per m² with a 10 mm trowel, for a standard cement-based adhesive. Lightweight adhesives use less; check the bag.

The figures are the middle of the ranges in MAPEI's Keraflex data sheet: a 20 kg bag covers 6–7.5 m² with a 6 mm square-notch trowel and 4–5 m² with a 10 mm one. Lightweight, high-yield adhesives use less: Schomburg MONOFLEX-XL, for example, quotes 1.6 kg/m² with a 6 mm notch, so use the figure on your bag. Larger tiles generally need a bigger notch, and back-buttering or an uneven floor uses more.

Laying tiles on a sand-cement bed instead? Work out the bed's cement and sand with the cement, sand and aggregate calculator.

Assumptions and limits

The calculator counts tiles on area and the joint. It doesn't plan the layout, so it can't see that a narrow strip at a wall wastes a whole tile.

• For rooms with many corners, columns or a pattern with borders, add to the waste allowance or tile each part as its own area.
• Tile sizes are used as entered. If the box gives an actual size that differs from the nominal one, enter the actual size.
• Grout and adhesive quantities are before any loss on site; MAPEI's grout calculator suggests adding 5–10%.
• Costs appear only for prices you enter. The calculator never guesses local prices.

Sources

Constants and limits come from these standards, manufacturers' data and trade bodies. Where practice varies, the calculator lets you change the value.

• Ultracolor Plus technical data sheet: grout consumption formulaMAPEI · current
• Keraflex technical data sheet: consumption by trowelMAPEI · current
• NIST Guide to the SI, Appendix B.9: conversion factorsNational Institute of Standards and Technology · SP 811

Found a value that doesn’t match your local practice? Tell us and we’ll review it.