Introduction
This Custom Building Products grout calculator tells you how much grout you need for a tile job. Type in your tile size, joint width, tile thickness, and the area you plan to tile. It returns the pounds or kilograms of grout to buy.
It also picks the right grout type for you. Thin joints need unsanded grout. Joints from 1/8 inch to 1/2 inch need sanded grout. Wider joints need a quarry-type grout. The calculator checks your joint width and names the match.
You can add more than one room, subtract spots you will not tile, like an island or a cabinet, and set a waste factor for cuts and spills. Then it compares bag sizes, counts how many bags you need, and flags the best price. A step-by-step section shows every part of the math, so you can check the work before you shop.
How to use our Custom Building Products Grout Calculator
Enter your tile size, joint width, and room area. The calculator tells you how much grout you need in pounds or kilograms, which grout type fits your joint, and how many bags to buy.
Grout Product Line: Pick Standard Grout or CustomTech Premium. Each one has its own density and bag sizes.
Unit System: Choose Imperial (inches, sq ft, pounds) or Metric (cm, m², kg). Your numbers change over on their own.
Bag Pricing: Type the price of each bag size. This is optional, but it lets the tool flag the cheapest bag to buy.
Tile Shape: Choose square, rectangle, hexagon, subway, or custom. The shape sets how the tile edges and face are measured.
Tile Size or Width: Measure one side of the tile face, not counting the joint. For hexagons, measure flat edge to flat edge.
Tile Length: For rectangle, subway, or custom tiles, enter the long side of the tile face.
Tile Thickness: Enter how thick the tile is. This is the depth of the grout joint. The default is 3/8 inch.
Grout Joint Width: Enter the gap between tiles, or drag the slider. This also sets the grout type: unsanded under 1/8 inch, sanded from 1/8 to 1/2 inch, and quarry type over 1/2 inch.
Coverage Areas: Name each room, then enter length and width, or type the total area. Click "Add Another Area" for more rooms.
Subtract Non-Tiled Spaces: Turn this on to take out islands, cabinets, or fixtures. Name each space and enter its area.
Waste Factor: Add extra grout for cuts, spills, and mixing loss. 10% works for most jobs. You can set 0% to 30%.
Show Weights In and Show Areas In: Pick the units for your results, such as pounds or kilograms and sq ft or m².
Press Calculate to see your grout weight, bag comparison, charts, and step-by-step math. Press Reset to start over.
Tile Grout: What You Need to Know
Grout is the paste that fills the small gaps between tiles. Those gaps are called joints. Grout locks the tiles in place, keeps water and dirt out, and makes the finished floor or wall look clean. Grout comes as a dry powder in bags. You mix it with water (or with a liquid additive) and press it into the joints with a rubber float.
What Changes How Much Grout You Need
Two jobs with the same square footage can need very different amounts of grout. Four things drive the number:
- Tile size: Small tiles mean more joints per square foot, so you need more grout. Large tiles mean fewer joints and less grout.
- Joint width: A wide joint holds more grout than a thin one.
- Tile thickness: The joint is as deep as the tile is thick. Thick tile means deeper joints and more grout.
- Tile shape: Squares, rectangles, and hexagons have different perimeters, so they create different amounts of joint length.
Picking the Right Grout Type
Joint width also tells you which grout to buy:
- Unsanded grout for joints under 1/8 inch. The sand in regular grout is too big to pack into a thin joint. Unsanded is also safer for soft, easy-to-scratch tile like polished marble and glass.
- Sanded grout for joints from 1/8 inch to 1/2 inch. The sand keeps the grout from shrinking and cracking as it dries. This is the most common choice for floors.
- Quarry or mortar-type grout for joints wider than 1/2 inch, like with slate, quarry tile, or rough stone. It has coarse sand that holds up in a big joint.
Why Add a Waste Factor
You will never use every bit of grout perfectly. Some sticks to the bucket and float, some is lost to cut tiles and odd joints, and some batches get stiff before you can use them. A waste factor of about 10% covers this. Go higher (15 to 20%) for small mosaic tile, lots of cuts, or a first-time job. Buying a little extra is cheaper than running out in the middle of a job, and a second bag may not match the first one in color.
Buying by the Bag
Grout is sold in set bag sizes, often 8, 10, or 25 pounds. You can only buy whole bags, so round up. Bigger bags usually cost less per pound, but not always. The cheaper choice depends on how many you need. Check the price per bag against how much grout will be left over.
Tips for a Good Grout Job
- Let the tile mortar cure fully before you grout, usually 24 hours or more.
- Mix only what you can use in about 30 minutes.
- Use the same water amount in every batch. Extra water makes the color lighter and the grout weaker.
- Wipe the haze off with a damp sponge, not a wet one.
- Seal cement grout after it cures to help it resist stains. Epoxy grout does not need sealing.
- Use caulk, not grout, where the floor meets a wall or where two walls meet.