How much extra tile should I buy?

10% waste is the standard for straight layouts. For diagonal or staggered patterns, buy 15% extra to cover cut tiles at the perimeter.

Why do I need to include the grout joint in the area?

Over a large room, the grout joint can account for 2-5% of the total area. Including it in the tile count calculation ensures you don't over-order by ignoring the "free" space between tiles.

What is "Die Lot" and why does it matter?

Tile colors vary slightly between manufacturing batches (die lots). Always buy your entire project from the same lot to ensure consistent color and sizing.

Surface Estimating

Tile Calculator

Accurately estimate the number of tiles, boxes, and total area for your tiling project. Include grout joint width for precise piece counts and factor in professional waste allowances for pattern alignment.

Tile Calculator

Estimate tiles and boxes for a rectangular floor (minus openings) with grout and waste

Waste allowance

Openings / non-tiled area

Room length

Room width

Box coverage (optional)

Tile length

Tile width

Grout joint

Results

Enter dimensions above to calculate

Calculating with Grout Joints

The "working" size of a tile includes the width of the grout joint. This is critical for calculating how many physical pieces are needed to fill a room.

Recommended Grout Widths

Tile Type	Joint Width	Design Rationale
Mosaic / Small format	1.5 mm (1/16")	Keeps focus on tile detail
Standard Wall / Floor	3.0 mm (1/8")	Industry standard for rectified tile
Large Format (60cm+)	5.0 mm (3/16")	Allows for substrate variations
Natural Stone / Rustic	6.0 mm+ (1/4"+)	Compensates for irregular tile edges

Step-by-Step Formulas

1. Net Installation Area

Net Area = Gross Area − Un-tiled Areas

Measure the floor or wall area to be tiled. Subtract areas for cabinets, tubs, or accent features that will use different materials.

2. Waste Factor

Order Area = Net Area × (1 + Waste%)

Add 10% waste for standard grid patterns. For diagonal layouts, herringbone, or complex patterns, budget 15–20% to account for more cut tile loss.

3. Individual Tile Area

Tile Area (sq ft) = ((Tile W + Joint) × (Tile H + Joint)) ÷ 144

The calculator includes the grout joint width in the area calculation of each tile. This gives a more accurate count of how many pieces fill the total area.

4. Box & Piece Counts

Pieces = ceil(Order Area ÷ Tile Area)

The total required area is divided by the sloped area of one tile. This provides the total number of pieces. If you enter the pieces-per-box value, the calculator will round up to the next full box.

Worked Example

Bathroom floor: 3 m × 2.4 m area, 300 × 300 mm tiles, 3 mm grout joint, 10% waste. 12 pieces per box.

Net Area = 3.0 × 2.4 = 7.2 m²

Order Area (+10%) = 7.2 × 1.10 = 7.92 m²

Working Tile Size = 303 × 303 mm = 0.0918 m²

Total Pieces = ceil(7.92 ÷ 0.0918) = ceil(86.27) = 87 pieces

Total Boxes = ceil(87 ÷ 12) = 8 boxes

💡 Professional Tiler's Tip

Before you begin, always dry-lay a row of tiles in both directions of the room to ensure you don\'t end up with narrow "slivers" (thin pieces of tile) at the edges. Adjust your starting position to balance the cuts on both sides of the room for the most professional appearance.

Frequently Asked Questions

How much extra tile should I buy?: 10% for straight patterns, 15% for diagonal or complex patterns like herringbone.
Does the calculator include grout joints?: Yes, it adds the grout joint width to the tile dimensions to provide an accurate piece count.
What is a "Die Lot"?: Batches of tile made at different times can vary in color. Order your entire project at once from the same batch to ensure a perfect match.