MEASURING AND BUYING GUIDE
How to calculate tiles for floors and walls
A useful estimate starts with reliable measurements, continues with the actual tile format and ends by adding an allowance for cuts, breakage and future repairs. This guide explains the criteria used by the calculator and the points to check before ordering.
Formula used
Net area ÷ area of one tile × 1.10 = recommended tiles
The area of one tile is its length multiplied by its width using consistent units. The final result is rounded up. The additional 10% is a general allowance; complex layouts may require more.
Quick example
A 10 × 12 ft room covers 120 ft². A 2 × 2 ft tile covers 4 ft²: 120 ÷ 4 = 30 net tiles. After adding a 10% allowance, the recommended purchase is 33 tiles.
Measuring step by step
1. Measure the area
For a floor, measure length and width. For a wall, measure width and height. Split complex spaces into simple rectangles or triangles and add their areas.
2. Find the net area
Multiply the dimensions of each section and add the results. On walls, doors, windows or niches can be deducted when their size is significant.
3. Keep units consistent
Do not mix metres, feet, centimetres or inches in one operation. For example, 8 ft 7 in equals 103 in and 5 ft 2 in equals 62 in; 103 × 62 ÷ 144 = 44.35 ft².
4. Check the format
Use the nominal dimensions of the selected tile and confirm the coverage printed on the box. Large tiles cover more area per piece but may create a different cutting plan.
5. Add allowance and boxes
Allow 5–10% for simple layouts and more for diagonal, herringbone or cut-heavy projects. Divide the recommended tiles by the number of pieces per box and round up.
Preparing a realistic budget
If you know the price per tile, multiply it by the recommended quantity. If the price is per m², multiply it by the purchase area including the allowance. Add adhesive, grout, trims, levelling accessories, tools, delivery and labour. A small contingency also helps cover breakage and later replacements.
Grout joints, rectified tiles and overlaps
A joint accommodates manufacturing tolerances and supports an even installation. Its width must follow the manufacturer and installation system; it may range from very fine joints near 1.5 mm to wider spacing for handmade products. Rectified tiles allow a less visible joint, but they should not be installed with no spacing unless explicitly permitted. For overlapping products such as some roof coverings, calculate the usable coverage rather than the outside dimensions.
Installation systems and patterns
Thin-bed cement adhesive
A common solution for prepared floors and walls, applied with a notched trowel suited to the tile format.
Mortar bed
Useful for levelling a base or forming falls, but it requires more depth, time and experience.
Ready-mixed adhesive
Practical for some internal wall coverings, but not suitable for every substrate or wet area.
Peel-and-stick products
Suitable for light refurbishment when the surface is smooth, clean and compatible.
Floating systems
Some products interlock over an underlay without adhesive and must follow their specific installation instructions.
Decorative patterns
A straight grid usually creates less waste. Diagonal, herringbone, staggered and mixed layouts produce more cuts and need a larger allowance.
Differences between floors and walls
For a floor, use length × width. For a wall, calculate width × height for each section and add them together. Openings may be deducted, while enough allowance should remain for edges, corners and changes in direction. Tile orientation and joint position also affect cuts.
Factors that change the result
- Actual area and measurement accuracy.
- Tile format and commercial box coverage.
- Laying pattern and direction.
- Corners, columns, openings and cut-outs.
- Joint width and product tolerances.
- Allowance for breakage and repairs.
Frequently asked questions about tile quantities
How do I calculate tiles for a floor or wall?
Calculate the net area, divide it by one tile's area, add the chosen allowance and round up. For walls, add each section and only deduct openings you have measured.
How many extra tiles should I buy?
As a guide, allow 5–10% for a straight layout. Use more for diagonal or herringbone patterns, extensive cutting or spare tiles kept for future repairs.
How many tiles cover 1 m²?
Divide 1 by one tile's area in m². A 60 × 60 cm tile covers 0.36 m², giving a theoretical 2.78 tiles per m² before allowance.
How do I calculate an area in feet or inches?
Multiply length by width in the same unit. Divide square inches by 144 to obtain square feet. The calculator converts ft² to m² internally before comparing it with a format in millimetres.
How do I calculate the number of boxes?
Divide the recommended tile count by the pieces in each box and always round up. Also check the manufacturer's stated coverage per box.
Does tile size affect the quantity?
Yes. Smaller formats require more individual pieces for the same area. Format also changes the cutting plan, so two layouts can need different allowances.
Can bathroom floor and wall tiles be calculated separately?
Yes, and this is usually clearer. Calculate the floor and each wall separately, especially when format, orientation, product or openings differ.
How do I estimate border tiles?
Measure the installation run and divide it by the usable length of each border piece. Add units for corners, junctions and cuts.
How should I measure an irregular room?
Split it into rectangles, triangles or other simple shapes. Calculate each area, add the total and then apply the tile format and allowance.
How do I estimate cost and labour?
Multiply the purchase quantity by the price per piece or per m², then add consumables, delivery and labour. Installation cost and duration depend on the substrate, pattern, format, location and site condition, so they require a professional quote.
This is an indicative estimate. Before ordering, confirm calibre, box coverage, batch, joint, adhesive and installation system with the manufacturer or the Ferragut technical team.
