Tile Grout Calculator

The Tile Grout Calculator works out exactly how much grout you need for a tiling job. Enter your tile size, the grout joint width and depth, and the total area, and it instantly returns the grout volume, the weight in kilograms and pounds, the number of bags to buy, and a coverage estimate. A live, scaled diagram shows your actual tile grid and joints so you can see at a glance how much surface the grout covers.

How Much Grout Do I Need?

The amount of grout depends on four things: how big your tiles are, how wide the joints are, how deep the joints are (usually the tile thickness), and the total area. Smaller tiles and wider joints mean more grout per square metre, because there is more joint length to fill. This calculator combines all four factors with the density of your chosen grout to give a buy-ready weight.

Tile Grout Formula

Grout volume is calculated from the fraction of the surface taken up by joints, multiplied by the joint depth and the area to be tiled.

The volume is then increased by your wastage allowance to give the total weight of grout to buy. Dividing by the bag size and rounding up gives the number of bags.

Recommended Grout Joint Widths

Sanded vs Unsanded vs Epoxy Grout

The grout type you choose does not change the joint volume, but it does change the weight of product because each has a different density.

How to Use This Calculator

1. Choose units and grout type: Pick metric or imperial, then select sanded, unsanded or epoxy grout.
2. Enter the tile and joint sizes: Type in your tile length and width, the joint width, and the joint depth (usually the tile thickness).
3. Enter the area: Add the total area to be tiled, an optional wastage allowance, and your bag size.
4. Click Calculate: Review the grout volume, weight, bags needed, the scaled tile diagram, and the full step-by-step breakdown.

Tips for an Accurate Estimate

• Measure the joint depth honestly. For most installations it equals the tile thickness; only use a shallower figure if you deliberately grout part-way.
• Round joints up, not down. Real joints are rarely perfectly even, so a slightly larger joint width gives a safer estimate.
• Always add wastage. A 10% allowance is normal; use 15% for big or intricate jobs and for hard-to-match grout colours.
• Buy whole bags of the same batch. Mixing batches can cause subtle colour differences, so it is worth buying a little extra up front.

Frequently Asked Questions

How is the amount of tile grout calculated?

Grout volume is found from the grout-line fraction of the surface multiplied by the joint depth and the area: Volume = ((Tile Length + Tile Width) / (Tile Length × Tile Width)) × Joint Width × Joint Depth × Area. The volume is then multiplied by the grout density to get the weight you need to buy.

What joint width should I use?

Typical joint widths are 2 to 3 mm (about 1/16 to 1/8 inch) for wall tiles and rectified floor tiles, and 3 to 5 mm (1/8 to 3/16 inch) for standard floor tiles. Larger or handmade tiles and outdoor paving often use 5 to 10 mm joints. Always follow the tile manufacturer's recommendation.

What is the joint depth?

The joint depth is how deep the grout sits between tiles. For most jobs it equals the tile thickness, so a 10 mm thick tile has a 10 mm deep joint. If you only grout the top portion of the joint, use that shallower depth instead.

How much extra grout should I buy?

Add a wastage allowance of about 10% to cover mixing losses, spillage, partial bags, and slightly uneven or wider joints. For large or complex jobs, or for hard-to-match coloured grout, 15% is safer so you do not run short.

Does sanded, unsanded or epoxy grout change the amount?

The joint volume is the same, but the weight of product differs because each grout has a different density. Sanded cement grout is the densest, unsanded is a little lighter, and epoxy sits in between. This calculator uses a representative density for each type to estimate the weight you need.

How many bags of grout do I need?

Divide the total grout weight (including wastage) by the weight of one bag and round up. For example, 18 kg of grout needed with 10 kg bags means you should buy two bags. Enter your bag size in the calculator to see the bag count automatically.

Additional Resources

• Grout - Wikipedia
• Tile - Wikipedia