acalculator

How much grout do I need?

Type the tiled area, the tile size and the joint width and depth. The grout calculator shows how much grout to buy in pounds, kilograms and bags. It works for Mapei grout and any other cement grout; this site is not linked to Mapei.

Your numbers

Units
Grout and bags
Grout (lb)
7.2

Buy 7.2 lb of grout; bags to buy: 1.

Grout (kg)
3.24
Bags to buy
1
Joint volume (L)
2.03
Grout per 100 ft² (lb)
6.5
Grout per m² (kg)
0.318

Grout (lb): 7.2. Buy 7.2 lb of grout; bags to buy: 1.

How to calculate

Computes how much tile grout to buy, in pounds, kilograms and bags, from the tiled area, tile size, joint width and depth, the grout’s density and a waste allowance.

Example with the default inputs (Area to grout 100 ft², Tile length 12 in, Tile width 12 in, Joint width 0.125 in, Joint depth 0.375 in, Grout density 99.8847369218314 lb/ft³, Extra for waste 10%, Bag size 25 lb): Buy 7.2 lb of grout; bags to buy: 1.

Method: Grout volume = area × (L + W) ÷ (L × W) × joint width × joint depth × (1 + waste ÷ 100); weight = volume × density; bags = weight ÷ bag size, rounded up.

  • Square-edged tiles laid in a grid, every joint the same width, filled to the joint depth (usually the tile thickness).
  • The density is how much grout powder fills a unit of joint volume. 1.6 kg/L (about 100 lb/ft³) is a typical cement grout figure; for the best estimate use the coverage chart or data sheet of your grout.
  • Waste is 10% by default, LATICRETE’s “10% rule”.
  • Bags are 25 lb (11.3 kg) by default, a common size for cement grout.

Machine-readable copies: Markdown, JSON.

Worked examples

Each example is checked against the calculator on every build.

  1. Area to grout 100 ft², Tile length 12 in, Tile width 12 in, Joint width 0.125 in, Joint depth 0.375 in, Grout density 99.88 lb/ft³, Extra for waste 0%, Bag size 25 lb gives Joint volume (L) 1.843545, Grout (kg) 2.949672, Grout (lb) 6.502913, Grout per 100 ft² (lb) 6.502913, Bags to buy 1.Source: Mapei group (Adesital), Grouts calculator (consumption from the volume to fill and the product density; inputs tile length, width, thickness and joint width). https://cms.mapei.com/adesital/en/product-calculator/grouts-calculator/
  2. Area to grout 107.6 ft², Tile length 11.81 in, Tile width 23.62 in, Joint width 0.1181 in, Joint depth 0.3937 in, Grout density 99.88 lb/ft³, Extra for waste 10%, Bag size 11.02 lb gives Grout per m² (kg) 0.24, Grout (kg) 2.64, Joint volume (L) 1.65, Bags to buy 1.Source: LATICRETE, Mastering Grout Calculation: The Power of the Grout Calculator (add at least 10% for waste). https://www.laticrete.com/blog/2023/october/the-power-of-the-grout-calculator
  3. Area to grout 400 ft², Tile length 2 in, Tile width 2 in, Joint width 0.125 in, Joint depth 0.25 in, Grout density 100 lb/ft³, Extra for waste 10%, Bag size 25 lb gives Grout (lb) 114.583333, Bags to buy 5.Source: LATICRETE, Cement Grouts FAQ (25 lb bags of sanded and unsanded grout). https://www.laticrete.com/support-and-training/downloads-and-faq/faqs/planning-a-job/cement-grouts

How it works

Tiles of length L and width W laid in a grid repeat every (L + j) by (W + j). Each tile owns one joint strip along its length and one along its width, so the joint area per tile is about j × (L + W) (the tiny j × j square where joints cross is left out, as maker formulas do). Per unit of tiled surface:

  • Joint volume per area = (L + W) ÷ (L × W) × j × d, where j is the joint width and d the joint depth
  • Grout volume = area × joint volume per area × (1 + waste ÷ 100)
  • Grout weight = grout volume × density
  • Bags = grout weight ÷ bag size, rounded up to a whole bag
  • Grout per 100 ft² and per m² = joint volume per area × density, without waste

Exact arithmetic. Each value is read as the exact decimal you typed, in the unit you typed it in (1/8 in typed as 0.125 in is exactly 3.175 mm), and every step is an exact fraction, so the bag count is an exact ceiling: a weight of exactly 2 bags is 2 bags, not 3. Unit sizes are exact: 1 in = 0.0254 m, 1 lb = 0.45359237 kg, 1 ft³ = 0.028316846592 m³, 1 lb/ft³ = 0.45359237 ÷ 0.028316846592 kg/m³.

Output format. Pounds show 1 decimal, kilograms, litres and pounds per 100 ft² 2 decimals, kilograms per m² 3 decimals, each rounded half up from its exact value, with trailing zeros left off. In Metric the answer leads with kilograms.

Assumptions

  • Square-edged tiles in a grid, every joint the same width and filled to the joint depth.
  • Density: 1.6 kg/L (1,600 kg/m³, about 99.9 lb/ft³) by default, a typical cement grout figure, not one maker’s product; type your grout’s figure.
  • Waste: 10% by default (LATICRETE’s 10% rule), 0% to 100%. Bags: 25 lb by default, 0.1 kg to 1,000 kg.
  • Tiles 1 mm to 10 m on a side; joints more than 0 and at most 10 cm wide and deep; areas up to 1,000,000 m².
  • This site is not affiliated with Mapei or LATICRETE.

Worked examples by hand

100 ft² of 12 × 12 in tile, 1/8 in joints, 3/8 in deep, 1.6 kg/L, no waste. (12 + 12) ÷ (12 × 12) × 0.125 × 0.375 = 0.0078125 in of joint per in² of surface. 100 ft² = 14,400 in², so the joints hold 112.5 in³ = 1.84 L; × 1.6 kg/L = 2.95 kg = 6.5 lb, 1 bag of 25 lb.

10 m² of 300 × 600 mm tile, 3 mm joints, 10 mm deep, 1.6 kg/L, 10% waste, 5 kg bags. (300 + 600) ÷ (300 × 600) × 3 × 10 = 0.15 mm = 0.15 L/m²; × 1.6 = 0.24 kg/m²; × 10 m² × 1.1 = 1.65 L = 2.64 kg, 1 bag.

400 ft² of 2 × 2 in mosaic, 1/8 in joints, 1/4 in deep, 100 lb/ft³, 10% waste, 25 lb bags. (2 + 2) ÷ 4 × 0.125 × 0.25 = 0.03125 in; × 57,600 in² = 1,800 in³; × 1.1 = 1,980 in³ = 1.1458 ft³; × 100 = 114.58 lb; ÷ 25 = 4.58, so 5 bags.

Other questions people ask

How do I calculate how much grout I need?

Each tile owns one length and one width of joint, so the joint volume per area is (L + W) ÷ (L × W) × joint width × joint depth. Multiply by the area and by the grout’s density to get the weight. For 100 ft² of 12 × 12 in tile with 1/8 in joints 3/8 in deep, that is 112.5 in³ of joint, about 6.5 lb of grout.

How does the Mapei grout calculator work out consumption?

The Mapei group’s grout calculator works from the volume to fill (tile length, width and thickness, joint width and area) and the product’s density. This page uses the same geometry; type the density from your grout’s data sheet for the closest match.

Why do small tiles need more grout?

Small tiles have more joint per square foot. A 2 × 2 in mosaic has 12 times the joint length of a 24 × 24 in tile over the same area, so with the same joints it needs 12 times the grout.

How much extra grout should I buy?

LATICRETE’s rule is to add at least 10% for waste during mixing and clean-up. The calculator adds 10% by default; then it rounds the bags up.

How deep is a grout joint?

Usually the full thickness of the tile, less any thinset that squeezed up into the joint. Use the tile thickness unless you know the joints are shallower.

What density should I use for grout?

The page uses 1.6 kg/L (about 100 lb/ft³), a typical figure for cement grout powder per volume of joint. Grouts differ: epoxy and lightweight grouts are lighter. Use the coverage chart or data sheet of the grout you buy.