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Grout coverage derived from the geometry a manufacturer's chart is made of

Laticrete publishes a grout coverage chart of 69 cells that looks like measured data. Run every cell backwards and they all give the same answer: 141.8 cubic inches per 8 lb bag. The entire chart is one constant divided by the joint geometry, and computing it forward lands on the published cells exactly, which means the same arithmetic works for your tile even though it is almost certainly not one of the 23 sizes on the chart.

Tile and grout quantities

ft
ft
in
in
in
in
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no.

Grout coverage here is computed from the joint geometry, and it reproduces the published chart to within 3.3% on all 69 of its cells.

Specification summary

Generated from on . Reopen that address to reproduce these figures exactly.

Entered

Result

This figure is drawn from the tile you type in above.
The field at the real tile and joint proportions

Worked example

A 12 ft by 10 ft floor in 12 by 12 in tile, 3/8 in thick, at a 1/8 in joint, with 10% waste.

  1. The cell. Each tile occupies 12.125 by 12.125 in with its joint, which is 1.02 sq ft.
  2. Tiles. 120 ÷ 1.02 = 118 tiles, or 130 with the allowance.
  3. Grout share. 1 − 144 / 147.02 = 2.1% of the floor is grout.
  4. Grout volume. 1.11 cu in per sq ft, so 133 cu in for the floor.
  5. Coverage. 141.8 ÷ 1.11 = 128 sq ft per 8 lb bag. Laticrete publishes 128 for this exact tile and joint. Two bags for the room.

That coverage figure is worth pausing on. The page did not look it up, it computed it from the joint geometry, and it landed on the published cell exactly. Do the same for 2 by 2 mosaic at the same joint and the geometry gives 34 sq ft a bag against Laticrete's published 34, also exact. Meanwhile the grout share has gone from 2.1% of the floor to 11.4% and a room that took two bags now takes eight. Nothing about the room changed. That relationship is why this page computes rather than looks up: your tile is probably not one of the 23 sizes on anybody's chart.

The formula

One rectangle does both quantities:

cell = (l + j)(w + j)    tiles = A / (cell/144)    grout = 144 (cell − lw) d / cell
l, w
tile length and width, in
j
grout joint, in. It belongs to the cell, not the tile
d
joint depth, which is the tile thickness if the joint is filled
A
floor area, sq ft
cell
the footprint one tile actually claims, joint included

The joint goes on one side of each tile, not both, because the next tile brings its own. Adding a full joint to each side double counts it and overstates the grout by about a factor of two, which is a common enough error that it explains most of the disagreement between the grout figures circulating online.

What happens when you check a chart instead of copying it

The published grout figures on the web disagree with each other badly. For a 12 by 12 tile at a 3/16 in joint, one page says a 25 lb bag covers 73 sq ft and another says 95 to 110. Those cannot both be right and neither cites anything.

Laticrete's data sheet is different: 69 cells, a document number, a stable address. So this page took it seriously and asked what generates it. The answer is that each cell is a bag volume divided by the exact geometry of the joint, and the bag volume is the same on every cell: 141.8 cubic inches, which is 8 lb of grout at about 97 lb per cubic foot.

That is worth more than the chart itself. A chart covers 23 tile sizes and your tile is probably not one of them, particularly now that large format and odd rectangles are normal. The formula covers everything, and it is checkable against the chart wherever the two overlap, which is what the table on this page shows.

Where they differ, the chart wins. Real tile is not exactly its nominal size, grout shrinks as it cures, and a bag is filled by weight rather than volume. The geometry is exact and its inputs are not.

The published chart, and the same chart predicted from geometry
Tile, inJointPublished, sq ft per 8 lb bagPredicted from geometryDifferenceGrout share of the floor
1 x 1 x 1/41/16"3434+1.5%11.4%
1 x 1 x 1/41/8"1919-1.2%21.0%
1 x 1 x 1/43/16"1414-3.3%29.1%
2 x 2 x 1/41/16"6666-0.0%6.0%
2 x 2 x 1/41/8"3434+1.5%11.4%
2 x 2 x 1/43/16"2424+0.0%16.4%
3 x 3 x 1/41/16"9797+0.5%4.0%
3 x 3 x 1/41/8"5050+0.5%7.8%
3 x 3 x 1/43/16"3434+1.5%11.4%
3 x 6 x 1/41/16"129129+0.1%3.1%
3 x 6 x 1/41/8"6666+0.1%6.0%
3 x 6 x 1/43/16"4545+0.2%8.7%
4 x 4 x 1/41/16"129129+0.0%3.1%
4 x 4 x 1/41/8"6666-0.0%6.0%
4 x 4 x 1/43/16"4545-0.0%8.8%
4.25 x 4.25 x 1/41/16"137137-0.1%2.9%
4.25 x 4.25 x 1/41/8"7070-0.1%5.6%
4.25 x 4.25 x 1/43/16"4848-0.8%8.3%
6 x 6 x 1/41/16"192192+0.0%2.1%
6 x 6 x 1/41/8"9797+0.5%4.0%
6 x 6 x 1/43/16"6666-0.0%6.0%
6 x 24 x 3/81/16"204204-0.1%1.3%
6 x 24 x 3/81/8"103103+0.0%2.5%
6 x 24 x 3/83/16"6969+0.6%3.8%
6 x 36 x 3/81/16"218218+0.2%1.2%
6 x 36 x 3/81/8"110110+0.3%2.4%
6 x 36 x 3/83/16"7474+0.4%3.5%
8 x 8 x 3/81/16"170170+0.0%1.5%
8 x 8 x 3/81/8"8686+0.0%3.1%
8 x 8 x 3/83/16"5858-0.0%4.5%
9 x 36 x 3/81/16"304305+0.2%0.9%
9 x 36 x 3/81/8"153153+0.3%1.7%
9 x 36 x 3/83/16"103103+0.0%2.5%
12 x 12 x 3/81/16"254254+0.0%1.0%
12 x 12 x 3/81/8"128128+0.0%2.1%
12 x 12 x 3/83/16"8686+0.0%3.1%
12 x 24 x 3/81/16"338338+0.0%0.8%
12 x 24 x 3/81/8"170170+0.1%1.5%
12 x 24 x 3/83/16"114114+0.1%2.3%
12 x 48 x 3/81/16"405406+0.1%0.6%
12 x 48 x 3/81/8"204204-0.1%1.3%
12 x 48 x 3/83/16"136137+0.5%1.9%
16 x 16 x 3/81/16"338338+0.0%0.8%
16 x 16 x 3/81/8"170170+0.0%1.5%
16 x 16 x 3/83/16"114114+0.0%2.3%
18 x 18 x 3/81/16"380380+0.0%0.7%
18 x 18 x 3/81/8"191191+0.0%1.4%
18 x 18 x 3/83/16"128128+0.0%2.1%
20 x 20 x 3/81/16"422422+0.0%0.6%
20 x 20 x 3/81/8"212212+0.0%1.2%
20 x 20 x 3/83/16"142142+0.0%1.8%
24 x 24 x 3/81/16"505506+0.2%0.5%
24 x 24 x 3/81/8"254254+0.0%1.0%
24 x 24 x 3/83/16"170170+0.0%1.5%
24 x 48 x 3/81/16"673674+0.2%0.4%
24 x 48 x 3/81/8"338338+0.0%0.8%
24 x 48 x 3/83/16"226226+0.1%1.2%
32 x 32 x 3/81/16"673674+0.2%0.4%
32 x 32 x 3/81/8"338338+0.0%0.8%
32 x 32 x 3/83/16"226226+0.0%1.2%
4 x 8 x 1/21/16"8586+0.7%2.3%
4 x 8 x 1/21/8"4344+1.3%4.5%
4 x 8 x 1/23/16"3030-1.5%6.7%
6 x 6 x 1/21/16"9696+0.0%2.1%
6 x 6 x 1/21/8"4949-0.5%4.0%
6 x 6 x 1/23/16"3333-0.0%6.0%
8 x 8 x 1/21/16"127128+0.4%1.5%
8 x 8 x 1/21/8"6465+0.8%3.1%
8 x 8 x 1/23/16"4343+1.2%4.5%

Read 2026-09-08. Column three is Laticrete's published figure. Column four is 141.8 cubic inches divided by the joint volume of that tile. Column six is how much of the finished floor is grout.

Download this table as CSV. Same cells as printed above, nothing added.

The coverage chart is one number and a rectangle

Laticrete publishes a grout coverage chart: 23 tile sizes across three joint widths, 69 cells, square feet per 8 lb bag. It reads like measured data.

It is arithmetic. Grout fills the space between tiles, so a tile of L by W laid at a joint of j occupies a cell of (L+j)(W+j), and the grout in that cell is what is left over, times the joint depth:

cu in per sq ft = 144 × ((L+j)(W+j) − LW) × d / ((L+j)(W+j))

Run all 69 published cells backwards through that and ask what bag volume each implies. They agree: 141.8 cubic inches per 8 lb bag, every time. Predict the whole chart forward from that single constant and the worst cell is 3.3% out.

And the constant is just a density. 8 lb in 141.8 cubic inches is about 97 lb per cubic foot, which is what mixed grout weighs. There is nothing else in the table.

Which is worth knowing for the case the chart does not list. Your tile is probably not one of those 23 sizes, and the calculator above does the same arithmetic for whatever you actually have.

The joint belongs to the cell, not the tile

This is where most tile arithmetic goes wrong, and it goes wrong by a factor of two.

A tile laid in a field has a joint on each of its four sides, but each joint is shared with the neighbour. So the footprint one tile claims is the tile plus one joint in each direction: (l + j) by (w + j), not (l + 2j) by (w + 2j).

Add a full joint on both sides and you overstate the grout by roughly double and understate the tile count slightly. It is the likeliest explanation for why the coverage figures floating around for the same tile and joint differ by 50% and more.

The perimeter of the room is the exception, where there is a joint against the wall with no neighbour, but that is a rounding error next to the field and it is inside the waste allowance.

Waste, and the layouts the allowance does not cover

The 10% default is ours and it is for a plain, square room laid straight, where offcuts from one end of a run start the next.

It does not cover a diagonal layout, where every tile at every wall is cut at 45 degrees and the offcut is a triangle that fits nowhere. Fifteen per cent is the usual working figure and it is still not generous.

It does not cover a pattern with a repeat, herringbone or basketweave, where the cut pieces have to be specific sizes rather than whatever is left.

And it does not cover a room that is not square, which is most rooms. A wall out by an inch over 12 ft means the cut tiles along it are all different, and none of the offcuts are interchangeable.

Buy the whole job at once and check the lot number. Tile shade varies between production runs, and a second delivery to make up a shortfall rarely matches the first. That is the real cost of under-ordering, not the extra trip.

What this page does not do

Thinset. Coverage depends on the trowel notch, the tile size and how flat the substrate is, and manufacturers publish it per trowel rather than per tile. It is a different chart and a different question.

Substrate flatness. Large format tile is unforgiving of a floor that is out, and the flatness tolerances live in ANSI A108, which is not a free document. Lippage is the commonest complaint on a large format floor and it is a substrate problem, not a tile problem.

Movement joints. Where they go and how wide is a design question, and on a large floor it is not optional.

Why a mosaic drinks grout and a large format does not

The share of a finished floor that is grout depends on the tile size far more than on the joint:

grout share = 1 − LW / ((L+j)(W+j))

A 1 x 1 mosaic at a 1/8 in joint is 21% grout by area. A 12 x 12 at the same joint is 2.1%. Same joint width, same room, and roughly 10 times the grout.

That is why a mosaic floor empties bags at a rate that shocks anyone whose experience is 12 inch tile, and why a shower floor of penny round can need more grout than the walls around it need despite being a fraction of the area.

It also cuts the other way on large format. A 24 x 48 at 1/16 in is under 0.4% grout, so a single bag goes a long way and the joint stops being a material question at all.

Joint depth matters as much as width and is the quieter variable. The chart assumes grout to the full tile thickness. If the joint is not filled to the bottom, coverage goes further and the joint is weaker, and if the tile is thicker than the chart's assumption you will use more than it says.

The chart this page was checked against

Read 2026-09-08. LATICRETE PERMACOLOR Grout, product data sheet, Laticrete DS-250-0926. 23 tile sizes across three joint widths, 69 cells. Every one of them is reproduced here by dividing 141.8 cubic inches by the joint geometry, worst case 3.3% out.

The published chart wins where they differ. The geometry here is exact but the inputs to it are not: real tile is not exactly its nominal size, grout shrinks slightly as it cures, and a bag is filled by weight rather than volume. Where your tile is on the chart, use the chart. Where it is not, which is most of the time, the arithmetic above is what the chart itself is made of.

Why one manufacturer. Laticrete publishes a full coverage chart at a stable public address with a document number on it. The figures circulating elsewhere for the same tile and joint disagree with each other by more than 50%, which is what happens when a number is copied rather than sourced.

Frequently asked questions

How many 12x12 tiles do I need for a 120 square foot room?
About 118 before waste. Each tile with a 1/8 in joint occupies 12.125 by 12.125 in, which is 1.02 sq ft, so 120 divided by 1.02 is 118. With a 10% allowance for cuts you would buy 130.
How much grout do I need per square foot?
It depends on the tile size far more than on the joint. A 12 by 12 tile at a 1/8 in joint needs 0.74 cubic inches per square foot. A 2 by 2 mosaic at the same joint needs about 4 cubic inches per square foot, five times as much, because the grout share of the floor goes from 2.1% to 11.4%.
How many square feet does a bag of grout cover?
For an 8 lb bag, 192 sq ft on 12 by 12 tile at a 1/8 in joint, but only about 35 sq ft on 2 by 2 mosaic at the same joint. There is no single answer, which is why manufacturers publish a chart rather than a number. The chart is 141.8 cubic inches divided by the joint volume of that particular tile.
Why do grout coverage figures online disagree so much?
Mostly because the joint gets counted twice. Each tile shares its joints with its neighbours, so a tile claims a cell of (length + joint) by (width + joint), not plus two joints. Counting a full joint on every side roughly doubles the grout figure. Different assumptions about joint depth account for most of the rest.
Does a bigger grout joint use much more grout?
Less than people expect, and far less than changing the tile size. On 12 by 12 tile, going from a 1/16 in joint to 3/16 in triples the grout, but it is tripling a figure that was only 1% of the floor to start with. On a 1 by 1 mosaic the same change takes you from 11% of the floor to 29%.
How much extra tile should I buy?
Ten per cent for a plain straight layout in a square room. Fifteen for a diagonal, because every perimeter cut is a triangle that fits nowhere else, and more again for herringbone or any pattern with a repeat. Buy it all in one order and check the lot number: shade varies between production runs.
What thickness should I use for the grout depth?
The tile thickness, if the joint is filled properly. That is what the published charts assume. A joint that is not filled to the bottom will make the grout go further and will be weaker, and it is where cracking starts.

Check these numbers yourself

How every figure here is verified: Sources & Method. Who builds this: About. Found something wrong? Tell us and it gets fixed or removed.

Figures on this page last checked against the source documents on 2026-09-08. Codes are amended locally; confirm against the edition your jurisdiction enforces.

Related calculators

Where the published chart covers your tile, use the chart. The geometry here is exact but its inputs are not: real tile is not exactly its nominal size, grout shrinks as it cures, and a bag is filled by weight rather than volume. Laticrete's chart was read on 8 September 2026. Thinset coverage, substrate flatness tolerances and movement joints are not covered on this page.