How much tile grout do I need?

Estimate grout from tile dimensions, joint width and depth, tiled area, and the product factor printed in the manufacturer’s consumption formula.

freeworks offlinenothing uploaded
ToolGrout Calculator
Input
Output
—
Put this on your own site

The frame below runs the same code as this page, in the reader's own browser. Nothing is sent to us, and nothing is sent to you.

Pick a dark background and the text and panels follow it, so the frame stays readable on a dark page.

Preview

How it works

Mapei’s formula multiplies tile perimeter relative to face area by joint depth, joint width, product factor, and tiled square metres. The mixing allowance increases that kilogram result before division by the selected pack size rounds up to whole packs.

Formula
kg/m² = (length + width) ÷ (length × width) × depth × joint width × K
  • The K factor is required because Mapei lists values from 1.4 to 1.6 across products in its published table.
  • Joint width, tile thickness, bag size, and allowance also have no universal defaults.

Worked example

10 square metres of 300mm tiles
8mm thick tiles, 3mm joints
Input
											Area m2: 10
Tile length mm: 300
Tile width mm: 300
Tile thickness mm: 8
Joint width mm: 3
Product factor: 1.6
Bag size kg: 5
Waste percent: 10
Output
												Grout kg exact: 2.56
Grout kg with waste: 2.82
Bags needed: 1

When to use this

Bathroom wall tiling, large-format floors, and epoxy-grout takeoffs each use the selected tile geometry and the matching product’s K factor.

Edge cases

  • Mosaics create far more joint length per square metre than 600 mm tiles, so equal tiled areas can have very different consumption.
  • A thicker tile or wider joint increases filled volume directly and is never inferred from a generic bathroom or floor label.
  • A requirement just above one selected pack rounds to two only after the entered mixing-loss allowance is applied.

References