ProjectFigure Exact material estimates for every home & DIY project.

Grout Calculator

A grout calculator estimates how much tile grout you need — in pounds and bags — from the tiled area, your tile size, the tile thickness and the width of the grout joints. Those four together decide grout use far more than area alone.

Your measurements

Result

Small mosaics with wide joints can need several times the grout of large-format tile over the same area, because there's so much more joint length. This works out the actual joint volume rather than guessing.

How it is calculated

Grout joint volume = area × joint width × tile thickness × (tile length + width) ÷ (length × width). Volume is converted to weight at ~115 lb/ft³ for cement grout. Coverage varies by grout type and trowel technique, so treat it as a buy-this-many-bags guide and round up.

Steps

Enter the tiled area.
Enter the tile length, width and thickness.
Enter the grout joint width you're using.
Read the pounds and number of bags.
Check the figure against your grout bag's coverage chart and buy one spare.

Worked example

100 sq ft of 12 × 12 in tile, 3/8 in thick, with 1/8 in joints needs roughly 8 lb of grout — one bag with spare.

Common questions

How much grout do I need?

It depends on tile size, thickness and joint width as well as area. The calculator combines all four — 100 sq ft of 12 in tile with 1/8 in joints is roughly 8 lb.

Why do small tiles use more grout?

More tiles means more total joint length, so mosaics and small tiles use far more grout per square foot than large-format tile.

Sanded or unsanded grout?

Sanded for joints 1/8 in and wider; unsanded for narrow joints and polished/soft tiles that sand could scratch. Coverage differs slightly — check the bag.

Should I buy extra grout?

Yes — buy at least one spare bag so the colour stays consistent and you can finish without a second store run.