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Grout Calculator

The joints you are actually filling, in pounds and in bags.

An estimate of quantity — the yield is worked back from one maker's chart; mixing loss is yours.

8' · 96 in · 8 ft · 2.4384 m

5' · 60 in · 5 ft · 1.524 m

80 ft²

Inch Calculator advises about 10% for tile laid straight, which is where this starts; 15% for diagonal, and Alpine 10-15% for herringbone. Mullican advises 5% for wood laid straight. It is added once, to whatever gets cut — the tiles or the planks, and the baseboard. A grout or mortar figure, where the page has one, is worked out on the surface as laid.

This page recalculates as you type. There is no Calculate button.

Answer

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Grout

4.32 lb

80 ft² to tile · 44 tiles · 6 boxes

Buy 44 tiles
Boxes 6 × box of 8
Area to tile 80 ft²
Ticked items cost $228.00
More numbers
With the 10% for cuts 88 ft²
Thinset 2 bags
DrawingThe project drawn to scale. Area 1: 8' × 5'.8'5'Area 1

Buying noteLarge tile wants mortar on the back of the tile as well as on the floor. Lift the first one back up and look at how much of it is covered before you set the rest.
Buying noteAt 1/8" buy sanded grout: unsanded is for joints under 1/8 in, and it cracks in a wider one. Our yield figure comes off the sanded chart, so this is the case it was worked out for.
Buying noteBuy the spare box with the rest, out of the same dye lot. A box bought a month later is a slightly different color, and nobody tells you until it is on the floor.

Breakdown

Surface Measurements Qty Area Share
Area 1 8' × 5' Add ×2 80 ft²

What to buy

Buying noteLarge tile wants mortar on the back of the tile as well as on the floor. Lift the first one back up and look at how much of it is covered before you set the rest.
Buying noteAt 1/8" buy sanded grout: unsanded is for joints under 1/8 in, and it cracks in a wider one. Our yield figure comes off the sanded chart, so this is the case it was worked out for.
Buying noteBuy the spare box with the rest, out of the same dye lot. A box bought a month later is a slightly different color, and nobody tells you until it is on the floor.

Shopping list

6 6 × box of 8 $186.00 Reference price $23.50. Type your store's. Reference price $31.00. Type your store's. Reference price $29.50. Type your store's. Reference price $30.00. Type your store's. Reference price $33.00. Type your store's. Reference price $28.00. Type your store's. Reference price $26.00. Type your store's. Reference price $42.00. Type your store's.
1 1 × 10 lb bag $14.00 Reference price $24.00. Type your store's. Reference price $14.00. Type your store's.
2 1 × 50 lb bag + 1 × 25 lb bag $28.00 Reference price $17.00. Type your store's. Reference price $11.00. Type your store's.
Ticked items $228.00

Untick what you already have. Each row has its price beside it — type what your store charges.

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Standards

We hold the criteria and the clause, not the wording of the standard.

Not checked ANSI A108.02 · minimum joint width, as CTEF reads §4.3.8

A 1/8" joint clears the 1/16" minimum, which is as far as a measurement gets. The clause also asks for three times how much the tiles vary across their faces — lay a few out dry and look before you commit to the spacers.

Not checked ANSI A108.02 · large format minimum joint, as CTEF reads §4.3.8.1

A 1/8" joint is the minimum for rectified tile and under the 3/16" a calibrated tile needs. Which one you have is printed on the box — no measurement here can tell us.

Not checked ANSI A108.02 · mortar contact, as CTEF reads A108.02

This project tiles a wall, so the standard asks for 95% of the back of each tile in contact with mortar, against 80% in a dry area. It is measured by lifting a set tile back off — nothing on this page can judge it.

How this was worked out

Every number below is yours. Each constant links to the row where you can change it.

Area 1 8' × 5' × 2 80 ft²
With the waste for cuts 80 ft² × (1 + 10%) 88 ft²
One tile and its joint (12 in + 1/8") × (24 in + 1/8") ÷ 144 in²/ft² 2.0314 ft²
Tiles to buy 88 ft² ÷ 2.0314 ft² 44 tiles
Boxes to buy 44 tiles ÷ 8 tiles 6 × box of 8 · 4 tiles left over
Grout 80 ft² × 0.8336 in³/ft² (1/8" joints, 3/8" deep) × 0.0648 lb/in³ 4.32 lb → 1 × 10 lb bag

Change:Tile thickness, floor tileGrout in a cubic inch

Thinset 80 ft² ÷ 60 ft²/bag 2 bags → 1 × 50 lb bag + 1 × 25 lb bag

Change:Thinset coverage, 1/4 × 3/8 notchBag the coverage is published for

What it comes to 6 × $31.00 + 1 × $14.00 + 1 × $17.00 + 1 × $11.00 $228.00

Assumptions

Every one of these is editable. Change one and the answer changes with it.

Assumption Value Confidence
Tile thickness, floor tile3/8 in, the nominal body thickness of porcelain floor tile 12 in and larger, and the thickness Custom Building Products' coverage chart lists a 12 x 24 at. Grout sits as deep as the tile is thick, so this number scales the grout straight; measure yours and type it. ~ in Derived or single-supplier
Grout in a cubic inch25 lb of grout fills about 386 in³ of joint, worked back out of 30 cells of Custom Building Products' Polyblend Plus Sanded coverage chart. A bag holds one volume whatever tile it goes into, so this is a density rather than a per-size figure. ~ lb/in³ Derived or single-supplier
Thinset coverage, 1/4 × 3/8 notch60 to 67 ft² a 50 lb bag with a 1/4 × 3/8 in square-notch trowel (TDS-119), the commonest notch for a 12 in and larger floor tile. The low end is the figure here. ft²/bag From a data sheet or an agency document
Bag the coverage is published forThe bag the coverage figures below are published for. Custom Building Products' TDS-119 states VersaBond coverage per 50 lb bag, so a 25 lb bag covers half as much: coverage scales with weight, and the page solves the order in pounds rather than in bags for that reason. lb/bag From a data sheet or an agency document
Minimum joint1/16 in, the smallest grout joint ANSI A108.02 allows, and never less than three times the tile's facial dimension variation. Read in the Ceramic Tile Education Foundation's article on the clause, not in the standard itself - ANSI charges for the text. in From a data sheet or an agency document
Minimum joint, rectified large format1/8 in, the smallest joint for rectified tile with an edge over 15 in. A rectified tile is ground to size after firing, so its edges are square enough for a narrow joint; a calibrated one is not. in From a data sheet or an agency document
Minimum joint, calibrated large format3/16 in, the smallest joint for calibrated tile with an edge over 15 in. Whether a box holds rectified or calibrated tile is printed on the box and is not something any measurement on this page can say, which is why the check that reads this number never passes on its own. in From a data sheet or an agency document
Edge at which large format starts15 in: above this edge length the minimum joint stops being 1/16 in and becomes 1/8 or 3/16 in depending on how the tile was made. A 12 x 24 is over it on one side, a 12 x 12 is not. in From a data sheet or an agency document
Mortar contact, dry area80% of the back of the tile has to be in contact with mortar in a dry area. It is measured by lifting a set tile back up, not by any number on this page, so the page says the figure rather than judging it. Held as a percentage because that is how it is read and how the box shows it. % From a data sheet or an agency document
Mortar contact, wet area95% mortar contact in a wet area - a shower, a tub surround - and outdoors. The higher figure is why a shower wall project is told a different sentence from a kitchen floor. Held as a percentage because that is how it is read and how the box shows it. % From a data sheet or an agency document

How much grout a tile job takes

Grout fills the joints, so the amount is the volume of the joints — and that is a shape, not a lookup. A joint runs round every tile, as wide as the spacer and as deep as the tile is thick. Work out the volume in one square foot and the whole floor is a multiplication.

For the 10 by 12 foot floor this page opens with, in 12 by 24 inch tile at 1/8 inch joints and 3/8 inch thick: 0.834 cubic inches of joint per square foot, which is 100 cubic inches over 120 square feet, or 6.5 pounds of grout. That is one small bag with a third of it left.

Where the formula comes from

Custom Building Products publish a coverage chart for Polyblend Plus: tile size down the side, joint width across, square feet a bag in the cells. It is a good chart and it has the same problem every chart has — your tile is between two rows, or off the end of them.

So we worked backwards out of thirty of its cells. At every tile 12 inches and over, the chart implies between 384 and 390 cubic inches of joint per 25 pound bag. Taking 386 puts this floor at 6.5 pounds, which is exactly what the chart's own cell says: 0.26 of a bag. The formula lands inside 1% of the chart across its whole large-format range, and then keeps working at sizes the chart does not list.

It runs over at the small end. A 2 by 2 inch mosaic has a great deal of joint for its area, and there our figure is about 20% above the chart's. The page says so on the tile where it happens, and it errs upward on purpose: a bag too many is an afternoon saved.

Sanded or unsanded

Joint Which grout
Under 1/8 inUnsanded
1/8 to 1/2 inSanded

Polyblend's own split. Unsanded grout in a wide joint shrinks and cracks; sanded grout in a narrow one will not pack in, and it can scratch a polished glaze. The page picks the one your joint calls for and names it on the shopping list. Our yield figure comes off the sanded chart, which is the nearest published number there is for either.

What changes the answer most

The joint, by a long way. Take the same floor from 1/8 inch joints to 1/4 inch and the grout roughly doubles, because the joint gets wider and the volume goes with it. Tile thickness is the other half: the same joint around a 1/4 inch mosaic holds two thirds of what it holds around a 3/8 inch porcelain. Both are boxes in the assumptions below, so if you have the box in front of you, type what it says.

Custom's own technical bulletin makes the point sharply: a change in joint width alone moves grout usage by about 25%. That is why this page asks for the joint rather than assuming one.