Figuring out how many tiles you need sounds straightforward until you are standing in the tile aisle staring at boxes labeled in square feet while your room measurements are in feet and inches. Get it wrong and you either run short mid-project or spend weeks trying to return unopened boxes of discontinued ceramic.
This tile calculator does the full math — room area, tile count with grout spacing, waste for your layout pattern, boxes to buy, grout quantity, and thinset bags. Enter your room dimensions and tile size below and get a complete shopping list in seconds.
🏠 Tile Calculator
Calculate tiles needed, boxes to buy, grout quantity, and total cost — with waste built in
Enter your room length and width in feet. Then enter your tile dimensions in inches. Select your grout line size — 1/8 inch is standard for most ceramic and porcelain floor tiles, while rectified tiles can go as tight as 1/16 inch. Natural stone typically needs 3/16 inch or wider.
The layout pattern matters more than most people realize. A straight grid wastes about 5% of material, while a herringbone pattern can waste 20% or more because so many edge cuts cannot be reused. The calculator adjusts waste automatically based on your pattern selection.
If you enter a price per box and tiles per box, the calculator will also estimate your total tile cost. The grout and thinset estimates are approximate — always buy one extra bag of each to avoid running short mid-project.
Tile Installation Checklists
The calculator tells you what to buy. The two checklists below tell you what to do with it. The supplies checklist covers every material and tool you need before you start — including subfloor prep items that many DIYers overlook until it is too late. The installation checklist walks through all three phases: layout planning, setting tiles, and grouting and finishing.
Proper substrate preparation is the most common cause of tile failure — more than adhesive or grout issues combined, according to the Tile Council of North America. The prep section of the checklist covers the steps most tutorials skip.
Straight grid generates the least waste at around 5%. Running bond (offset rows like brickwork) adds about 10% waste from edge cuts. Diagonal installations at 45 degrees require 15% extra. Herringbone is the most demanding at 20% or more. For any complex or custom pattern, budget 25% waste and consider hiring a professional installer. OSHA also recommends wet-cutting methods and respiratory protection when cutting tile to minimize silica dust exposure.
Frequently Asked Questions
How do I calculate how many tiles I need?+
Multiply the room length by the width to get square footage. Divide that by the square footage of one tile. Then add a waste percentage — 5% for straight grid layouts, 10% for running bond, 15% for diagonal, and 20% for herringbone. Always round up to whole tiles. The calculator above handles all of this automatically including grout line spacing.
How much extra tile should I buy?+
Buy at least 10% extra for a straight grid installation — 15% for diagonal and 20% for herringbone. Extra tiles cover cuts, breakage, and future repairs. Once a tile line is discontinued, matching it years later is nearly impossible. Keeping a few extras on hand is always worth the small upfront cost.
What is the standard grout line size for floor tiles?+
The standard grout line for most ceramic and porcelain floor tiles is 1/8 inch (3mm). Rectified tiles can use as little as 1/16 inch for a near-seamless look. Natural stone tiles typically use 3/16 inch or wider to accommodate slight variations in size. Large format tiles generally use a 3/16 to 1/4 inch grout line.
How much thinset mortar do I need?+
A standard 50-pound bag of thinset covers approximately 40 to 50 square feet depending on tile size and trowel notch depth. Larger tiles require a larger notch trowel which uses more mortar per square foot. The calculator above estimates the number of bags for your project. Always buy one extra bag to avoid running short mid-installation.
Can I tile over existing tile?+
Yes, in most cases you can tile over existing tile if it is solidly adhered, flat, and the added height will not cause issues with doors or transitions. Clean the existing tile thoroughly, apply a bonding primer or polymer-modified thinset, and proceed normally. If any existing tiles are loose or sound hollow when tapped, remove them before starting.
Where should you use caulk instead of grout?+
Never use grout in corners where two tiled surfaces meet — floor to wall, wall to wall, or tile to tub. These joints need flexible caulk because the surfaces expand and contract at different rates. Grout in corners will crack within months. Use a color-matched caulk that blends with your grout color for a seamless look.
How long before you can walk on new tile?+
Most thinset requires 24 hours before light foot traffic. Wait 48 to 72 hours before grouting, and another 24 to 48 hours after grouting before normal use. For shower floors, allow 72 hours minimum before exposing to water. Always check your specific product instructions as cure times vary by brand and conditions.
Do I need cement board under tile?+
Yes for any wet area — showers, bathroom floors, and areas near water. Cement board prevents moisture from damaging the subfloor and gives tile a stable, rigid surface. For dry areas with a solid plywood subfloor in good condition you may tile directly, but cement board is always the safer choice. Never tile over OSB or particle board.
🛒 Tile Installation Supplies
Everything you need to complete your tile project — all available on Amazon.
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Tile Wet Saw
A wet saw is essential for clean, accurate cuts on ceramic, porcelain, and natural stone tile. Makes diagonal cuts and notches easy.
