Ordering too few tiles means a frantic search for matching stock. Ordering too many wastes money. The right calculation requires four steps — and this guide walks you through each one with worked examples for Indian rooms.
Why Getting the Quantity Right Matters
Running short of tiles mid-project is one of the most avoidable and frustrating mistakes in home renovation. Tile batches are fired at specific kiln temperatures for specific durations, and even the same design from the same factory will have slight shade variations between production runs. If you top up from a newer batch, the colour match is rarely invisible — particularly in light shades.
Over-ordering wastes money on materials you can't return. The goal is the calculated amount plus the right wastage buffer. This guide shows you how to arrive at that number.
Step 1: Measure the Room Area
For rectangular rooms, multiply length by width. You can measure in feet or metres but stick to one unit throughout.
For L-shaped or irregular rooms, divide the space into rectangles, calculate each one separately and add them up. Sketch it out on paper first — it prevents the kind of errors that cost money.
For walls, measure height by width for each wall you're tiling. If you're tiling all four bathroom walls to 7 feet high, calculate each wall separately and total them.
Pro Tip
Measure twice, always. One wrong number compounds through every calculation that follows. For walls, measure at both the base and the top edge of the tiled area since older buildings are rarely perfectly plumb and the width can vary by 10 to 20mm between floor and ceiling.
Step 2: Deduct Fixed Obstructions
For floors, you generally don't need to deduct for thin obstructions like columns or pillar bases.
For walls, deduct door and window openings within the tiled zone. A standard Indian interior door runs about 3x7 feet (21 sq ft) and a typical window around 4x4 feet (16 sq ft).
There's a counter-consideration worth knowing: deducting obstructions reduces your order, but the cuts around those same obstructions generate more wastage. In small rooms with multiple windows and doors, it's often safer to skip the deductions and let the wastage allowance absorb the extra cutting.
| Obstruction | Typical Size | Deduct? |
|---|---|---|
| Interior door opening | 3×7 ft = 21 sq ft | Yes, if room is large (200+ sq ft) |
| Window opening | 4×4 ft = 16 sq ft | Yes, if room is large (200+ sq ft) |
| Built-in wardrobe base | Varies | Yes for floor tiles only if full-depth |
| Column / pillar | Varies | No — tile cuts around it generate wastage |
| Bathtub | Approx 5×3 ft = 15 sq ft | Yes for floor tile under bath area |
Step 3: Add Wastage Allowance
Every tile installation generates some wastage. Tiles get cut at every edge, corner and obstruction, and those offcuts can't be used elsewhere. Add in handling breakage and the total climbs further.
The right wastage percentage depends on tile size, room complexity and the laying pattern.
| Situation | Wastage to Add |
|---|---|
| Simple rectangular room, straight lay | 5% – 8% |
| Rectangular room with obstacles | 8% – 12% |
| L-shaped or irregular room | 10% – 15% |
| Diagonal (45°) tile layout | 15% – 20% |
| Herringbone or basket-weave pattern | 15% – 25% |
| Large format tiles (600×1200mm+) | 10% – 15% |
| Natural stone (marble, slate) | 10% – 15% |
Pro Tip
When in doubt, use 12% wastage as your default. It covers most standard Indian room installations. For diagonal or pattern layouts, use 18%. These percentages have been validated across thousands of projects.
The Complete Formula
Here is the complete tile quantity calculation in three lines:
Net Area = Room Length × Room Width (minus any large obstruction deductions)
Gross Quantity = Net Area × (1 + Wastage %) — Example: 200 sq ft × 1.12 = 224 sq ft
Boxes Needed = Gross Quantity ÷ Coverage per Box (check the box label — typically 8 to 12 sq ft per box). Always round UP to the nearest whole box.
Worked Example 1: Master Bedroom Floor (Indian Standard)
Room dimensions: 15 feet × 12 feet
Tile size: 600×600mm (24×24 inches). Box coverage: 10.76 sq ft (4 tiles per box)
Tile pattern: Straight lay
Net Area = 15 × 12 = 180 sq ft
No deductions (bedroom floor, no large obstructions)
Wastage: 10% (straight lay, slight complexity near wardrobes)
Gross Quantity = 180 × 1.10 = 198 sq ft
Boxes = 198 ÷ 10.76 = 18.4 boxes → Round up to 19 boxes
Order 19 boxes. Keep leftover tiles stored with the original batch number for future repairs.
Worked Example 2: Bathroom Wall Tiles
Bathroom dimensions: 8 feet × 6 feet. Tile height: 8 feet (floor to ceiling)
Tile size: 300×600mm (12×24 inches). Box coverage: 9 sq ft
Two doors (no windows). Door size: 3×7 ft
Wall areas:
Wall 1: 8 × 8 = 64 sq ft
Wall 2: 8 × 8 = 64 sq ft
Wall 3: 6 × 8 = 48 sq ft
Wall 4: 6 × 8 = 48 sq ft (minus 1 door: 3×7 = 21 sq ft) = 27 sq ft
Total Wall Area = 64 + 64 + 48 + 27 = 203 sq ft
Wastage: 12% (multiple cuts around fixtures, door frame, corners)
Gross Quantity = 203 × 1.12 = 227 sq ft
Boxes = 227 ÷ 9 = 25.2 → Round up to 26 boxes
Pro Tip
For bathroom walls, always buy one extra box beyond your rounded-up calculation. Tiles break more readily on walls (thinner than floor tiles), and the intricate cuts around fixtures and fittings generate more breakage than flat floor installation.
One More Step: Keep Spare Tiles
After the job is done, store 3 to 5 percent of the total order. Those tiles are your insurance for future cracks, or for extending the same surface into a new area like a built-in shelf or an additional wet zone.
Write the batch number and purchase date on the box and store it flat in a dry spot. Natural stone and Italian marble leftovers are especially worth holding onto — the exact vein pattern from your slab block can't be replicated.
Frequently Asked Questions
How many tiles do I need for a 10×10 foot room?
A 10×10 room is 100 sq ft. With 10% wastage allowance, order for 110 sq ft. The number of boxes depends on your tile size: 600×600mm tiles give 4 tiles per box (10.76 sq ft/box) — you would need 11 boxes. Check the box label for exact coverage.
How do I calculate tiles for a room in square metres?
Measure length × width in metres. Multiply by 1 + wastage percentage. Divide by the tile area in square metres (e.g., a 600×600mm tile = 0.36 sq m; a box of 4 = 1.44 sq m). Round up to whole boxes. 1 sq metre = 10.76 sq ft — you can convert either way.
Should I include the area under kitchen cabinets when calculating floor tiles?
Yes. Even though the tiles under base cabinets will not be visible, they must be installed before cabinets are fitted to ensure a level, moisture-resistant base. Deducting that area causes a shortfall if cabinets are ever moved.
What if I ordered too many tiles?
Most tile showrooms do not accept returns on opened boxes or on tiles from specific production batches. Unopened boxes may be exchanged within 30 days with the original invoice. Always check the showroom's return policy before purchasing. This is another reason to calculate carefully rather than over-ordering speculatively.
How does diagonal tiling increase wastage so much?
When tiles are laid at 45° to the room walls, every edge of the room creates half-tile triangular cuts. These triangular offcuts cannot be used elsewhere and are discarded. The cuts along all four walls of a room add up to approximately 15–20% of the total tile area — significantly more than the 5–8% for straight lay. The visual impact is worth it in many designs, but budget accordingly.
Still have questions?
Our team at The Tile Museum will guide you in person.