Tile Grout Calculator
Enter your tile size, joint width, and the area you're tiling to find out exactly how many kilograms of grout you need and how many bags to buy. Includes a recommendation on sanded vs unsanded grout and a tile pattern preview. Nothing uploaded.
Tile and joint settings
Results
Learn more: tile grout calculations and sanded vs unsanded
Why guessing grout quantity always goes wrong
The amount of grout you need depends on three things: the tile size (which determines how many linear metres of joint there are per m2), the joint width, and the tile thickness. A 100x100 mm tile has roughly five times more joint length per m2 than a 500x500 mm tile. A 5 mm joint needs five times more grout than a 1 mm joint. Get either factor wrong and you either run out mid-job or buy far too much. The calculator uses the exact volumetric formula - joint cross-section area times joint length per m2 times tile thickness - to give a precise figure before you buy anything.
Sanded vs unsanded grout and why 3 mm is the threshold
Use sanded grout for joints 3 mm (1/8 inch) or wider. Sanded grout contains fine sand particles that fill the joint and prevent shrinkage cracking. Use unsanded grout for joints narrower than 3 mm - the sand particles can scratch polished or delicate tile surfaces and the mix is too coarse to flow into narrow gaps. Epoxy grout is denser than cement-based grout and resists staining and chemicals much better, but it is harder to work with and covers slightly less volume per kilogram.
Waste factor and how to avoid running out mid-job
A waste factor of 10 percent is standard for straight rectangular layouts. Diagonal patterns, complex cuts, and awkward edges require 15 percent. Always round up to the nearest whole bag size and buy one extra bag for future repairs. A 5 kg bag of grout lasts a long time when stored correctly, so there is no risk in over-buying slightly.
FAQ
How much grout do I need per m2 of tiles?
It depends on tile size and joint width. For 300x300 mm tiles with a 3 mm joint, you need approximately 0.45-0.55 kg per m2 of standard grout. Smaller tiles or wider joints need more grout because there is more joint area relative to tile area. The calculator gives an exact figure for your specific tile and joint dimensions.
Should I use sanded or unsanded grout?
Use sanded grout for joints 3 mm (1/8 inch) or wider. Sanded grout contains fine sand particles that fill the joint and prevent shrinkage cracking. Use unsanded grout for joints narrower than 3 mm - the sand particles can scratch polished or delicate tile surfaces and the mix is too coarse to flow into narrow gaps.
How do I calculate how many bags of grout I need?
Divide the total grout weight (including your waste factor) by the bag size. For example, if you need 4.5 kg of grout: one 5 kg bag is enough, but two 3 kg bags also cover it. Always buy one bag extra as a precaution against waste and future repairs.