Grout and Mortar Calculator

Joint volume from the tile grid, bags from yield, nothing from vibes

Grout and mortar are bought by the bag and consumed by the cubic inch, and the bridge between them is geometry plus yield: the joint volume in a tiled floor follows the grid exactly (tile size, joint width, joint depth), a repointing job is a length of joint cross-section, a mortar bed is an area at a thickness, and brick and block laying follows the trade’s bag rates. This calculator runs all four honestly: volumes computed from the dimensions you give, converted to bags at the yield or density printed on your product, with a waste allowance you set, because the only dishonest version of this estimate is the one hiding a universal coverage number for every tile and joint ever made.

Disclaimer: This calculator gives estimates for general information only. It is not financial, medical or other professional advice. Mortar type selection (N, S, M and others) follows structural requirements and code, not quantity; manufacturers’ yields and mixing instructions govern on site.

What this calculator does

Each mode follows its material’s real consumption model. Grout fills a grid, so its volume is the grid’s: every tile carries its length plus its width of joint (the other two sides belong to the neighbours’ accounting), at your joint width and depth, summed over the area. Repointing consumes a cross-section along a length. A bed consumes an area at a thickness. Laying consumes bags at rates the trade plans by, since a laid joint’s volume depends on the mason’s hand more than on paper geometry. All four then pass through the same honest exit: your product’s yield or density, your waste figure, whole bags.

How to use it

  • Joint depth for grout is the tile’s thickness, less a hair. Tooled grout sits slightly below the tile face, so full thickness is the conservative figure and the waste allowance absorbs the difference; cushioned-edge tiles hold more grout than the grid says, which the limitations flag.
  • Yield comes off the bag. Mortar and grout yields per bag are printed data; a 60 lb bag of mortar mix yields roughly 0.45 cu ft mixed. Site-mixed mortar from cement, lime and sand is the same volume bought as ingredients, and the volume line is what you batch from.
  • Repointing depth is the ground-out depth. Sound work rakes joints to about twice the joint width or until sound mortar; measure the depth you actually cut, since the volume follows it exactly.
  • Waste on mortar is pot life, not just spillage. Mix beyond what the crew places inside the working window becomes waste by the clock; smaller batches at a slightly higher nominal waste figure is the professional pattern this field quietly encodes.

The methods

  • Grout volume per sq ft = (tile length + tile width) × joint width × joint depth / (tile length × tile width) × 144, in cubic inches. Dry weight = volume × the mixed density entered; bags by your bag size, waste applied first.
  • Repointing volume = joint length × width × depth. Bed volume = area × thickness. Bags = volume / bag yield, waste applied, rounded up.
  • Laying: bags = units × the stated planning rate for the unit (the same rates the masonry calculator on this site prints), rounded up.

Worked examples

The bathroom floor. One hundred square feet of 12 × 12 tile at a 0.25 in joint, 0.375 deep: each square foot holds 2.25 cu in of joint, so the floor takes 225 cu in, 0.13 cu ft, about 15.63 lb of grout at the planning density, 17.19 lb with 10 percent waste, and therefore a single 25 lb bag with room to spare. The same floor in 2 in mosaics would take roughly three times the grout, which is the grid formula’s favourite party trick and the reading section explains it.

The mortar bed. A 100 sq ft shower pan bed at 1.5 in is 12.50 cu ft of mortar; at a 0.45 cu ft yield that is 28 bags of 60 lb mix, a number that surprises everyone exactly once, at the estimating stage if this page does its job, or at the driveway if it does not.

The repoint. Two hundred feet of 3/8 in joint ground out 3/4 deep is 675 cu in (0.39 cu ft), one bag at the same yield before waste, plus the discipline of the method: repointing quantities are small and labour is the cost, which the figures state plainly by being small.

Reading your results

Read grout results against tile size instinctively after one use: halving the tile quadruples the joint length per square foot, and grout consumption follows, which is why mosaic floors drink grout and large-format floors sip it. Read mortar volumes as batch planning as much as purchasing (the cu ft line divides into mixer loads). And read the laying rates as planning figures with the mason’s variation inside them, never as a specification: the joints a crew actually strikes are the yield you actually get.

Limitations

  • Tile edges change the joint’s true shape. Cushioned and bevelled edges widen the joint at the surface, handmade tiles vary in size so joints vary with them, and grout also keys into the tile’s back pattern at edges; real consumption runs above the grid’s clean geometry, which is what the waste field is for.
  • Density and yield are product data. Polymer-modified and epoxy grouts depart from the cementitious planning density entirely (epoxy is bought by the unit kit against manufacturer coverage charts); use the product’s own figures in the fields provided, or its chart instead of this page.
  • Mortar type is not a quantity. Type M, S and N differ in strength and duty, and choosing between them is structural and code business; this page counts bags of whichever type the design specifies and takes no part in the choice.
  • Structural repairs are not repointing arithmetic. Cracked joints from movement, failed lintels or water damage need the cause addressed; fresh mortar in a joint that is still moving is a recurring subscription, not a repair.

Frequently asked questions

How much grout do I need for tile?

The grid decides: joint length per square foot times width times depth. For the common case (12 in tiles, quarter-inch joints, 3/8 thick) it is about 0.16 lb per square foot at cementitious density, so a 25 lb bag serves roughly 150 sq ft before waste, and the worked example shows the full chain. Shrink the tile or widen the joint and the figure climbs steeply, which is why grout charts are printed per tile size and joint, and why this calculator takes yours instead of quoting one row of somebody’s chart.

How many bags of mortar do 100 blocks take?

At the planning rate used here, about 9 bags of 60 lb premix per 100 standard blocks, and about 2.2 bags per 100 modular bricks: the same rates the masonry calculator applies, printed openly so a mason’s own figure can replace them. Site-mixed mortar for the same wall is roughly 0.9 bags, about 0.41 cu ft of mixed mortar, per 10 blocks at these rates, batched from cement and sand in the proportions the specified type requires.

Why did my grout run out mid-floor?

Almost always one of three arithmetic ambushes: the tile was smaller than the chart row used (joint length per square foot doubles when tile size halves), the joints were wider or deeper than the plan (volume follows both, multiplicatively), or the tile’s cushioned edges quietly enlarged every joint. The prevention is the method on this page: measure the actual tile, joint and thickness going in, and let the waste figure cover the edges rather than the dimensions being wrong in the optimistic direction on all three axes at once.

Can I mix half bags and keep the rest?

Dry product keeps if it stays dry, so partial bags are a storage question (sealed, off the floor, used within the product’s shelf life); mixed product does not keep at all, and retempering beyond the manufacturer’s allowance trades strength for convenience invisibly. Batch sizing is the real skill the volume line supports: mix the cu ft the crew can place inside the working window, and the waste figure shrinks to honest spillage.

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Method: grout volume from the tile grid geometry, mortar volumes from joint cross-sections and bed areas, laying from stated trade bag rates, all converted at user-entered yield or density with waste. Last reviewed: 15 October 2026.