Grout Calculator
Enter the area to tile, the size and thickness of the tile and the joint width to estimate how many pounds of grout you need. Grout density is editable because products differ.
How to use this grout calculator
- Enter the area you will tile in square feet.
- Enter the length and width of one tile and its thickness in inches. Grout fills the joint to about the thickness of the tile.
- Enter the joint width. Common joints are small, and your layout may call for a wider one.
- Keep the default grout weight or enter the figure from your product, then set a waste allowance and the bag size.
- Press Calculate. Use Copy result to keep the figures.
How to calculate how much grout you need
The calculator finds the volume of the joints and turns it into weight using the grout weight you enter.
- Joint volume per sq ft = 144 x (tile length + tile width) x joint width x thickness / (tile length x tile width), in cubic inches
- Total joint volume = joint volume per sq ft x area
- Grout weight = joint volume x weight per cubic inch x (1 + waste % / 100)
- Bags = grout weight / bag size, rounded up
Worked example
You are tiling 100 sq ft with 12 in by 12 in tiles, 0.375 in thick, with 0.125 in joints. The joint volume per square foot is 144 x 24 x 0.125 x 0.375 / 144 = 1.125 cubic inches. For 100 sq ft that is 112.5 cubic inches. At 0.065 lb per cubic inch, that is 7.31 lb, and with 10% waste you need 8.0 lb. A 10 lb bag is enough, so you buy 1 bag.
Assumptions & limits
- The joint is filled to the full thickness of the tile and each tile has joints on all four sides, shared with its neighbors.
- The default grout weight is an editable placeholder. Products differ in density, water content and how they pack, so use the figure from the data sheet if you have one.
- Real jobs use more grout than the joint volume alone because of waste, uneven tile, and cleanup. The waste percentage covers this.
- Rough or irregular tile, such as natural stone with deep texture, can use much more grout.
- The package coverage chart from the maker is the best final check.
Frequently asked questions
How do I calculate how much grout I need?
Find the volume of the joints from the tile size, joint width and thickness, then convert it to weight with the grout density. The calculator does this and adds waste.
How much grout do I need for 100 square feet?
It depends on the tile size, thickness and joint width. For 12 inch tiles, a 0.375 inch thickness and a 0.125 inch joint, the estimate is about 8 lb with waste. Smaller tiles need more.
Why do small tiles need more grout?
Small tiles have more joints per square foot, so more joint volume has to be filled.
What joint width should I use?
It depends on the tile and the layout. Follow the tile maker and the grout maker. The calculator uses the width you enter.
Is the grout weight accurate for every product?
No. It is an editable placeholder. Check the data sheet of your product for yield and coverage.
Should I buy extra grout?
A little extra is wise. The waste allowance is meant for this, and you can raise it for rough tile.
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Last updated: November 2026