How many bags of mortar do I need?

Divide your block or brick count by how many one bag lays, then round up. A bag of mortar mix lays roughly a dozen standard blocks or around thirty-odd bricks, though both depend on the bag size and the joint. Enter your count and the units-per-bag figure above and the bag tally, with a little waste, appears at once.

How many blocks does a bag of mortar lay?

For a typical 80 lb bag of mortar mix, on the order of twelve to fourteen standard blocks with a normal joint — a smaller metric bag lays fewer. It is the editable default here rather than a fixed figure, because a wider joint, a rougher block or a leaner mix all change it. Set it to what your supplier quotes.

Does the joint size matter?

A great deal. A thicker bed and head joint uses more mortar per unit, so fewer units come off each bag. That is exactly why the units-per-bag figure is a field you set rather than a number baked in — dial it down for a fat joint, up for a tight one, and the bag count follows.

Should I round bags up?

Always, and the tool does. You buy whole bags, running out mid-course means a cold joint, and mixing a fresh bag late in the day is a nuisance. A spare bag on the pallet is cheap insurance against stopping the wall short of the top.

Mortar calculator

Matériau posé

Nombre d’éléments

Format du sac

Le sac que vous achetez — 80 lb et 25 kg sont courants.

Éléments par sac

Selon votre fournisseur, pour ce sac — l’épaisseur des joints le détermine.

Facteur de perte

Supplément pour ce qui tombe de la planche à mortier et pour les joints que vous rejointoyez.

— sacs à acheter

Garder ces résultats

Nous envoyons ce seul courriel par notre fournisseur de courriel et ne gardons pas votre adresse.

This turns a unit count into a bag count using the yield you set. Real coverage swings with the joint, the mix and the weather, so keep a spare bag rather than trusting the tally exactly. It is a materials estimate, not a mix design or a structural spec.

Pick whether you are laying block or brick, enter how many and how many one bag lays, and the tool divides the count by the yield, adds a waste margin and rounds up to whole bags of mortar mix.

Exemple détaillé

Laying 150 blocks, with a bag good for about 13 blocks: 150 ÷ 13 ≈ 11.5 bags. Add 10% for waste and round up and you would buy 13 bags. Switch to brick at, say, 35 per bag and 600 bricks would need 600 ÷ 35 ≈ 18 bags before waste.

With 25 kg bags, where this page's default is about 8 blocks a bag: 150 ÷ 8 = 18.75 bags, 20.6 with 10% waste — buy 21. Brick at 22 a bag puts 600 bricks at 27.3 bags before waste.

Sur le chantier

The foundation from the block page. 816 blocks at 13 a bag is 62.8 bags, and with 10% it is 69.05 — whole bags only, so 70. The rounding did that on its own; what the yard's pallet decides is whether you buy 70 or the next whole pallet above it. The block count comes off the block tool; this page only divides it by what a bag lays.

Where the yield really comes from. "13 blocks a bag" is this page's default for a ⅜ in joint on a standard block. A ½ in joint uses a third more mortar per joint (in metric, a 12 mm joint about a fifth more than a 10 mm one), a hot day dries the board faster and a green apprentice drops more off the trowel. Ask the supplier what their bag lays for your joint, type it, and set the waste to the crew you actually have.

Brick veneer, by the thousand. 3,050 bricks at 35 a bag is 87.1, × 1.1 = 95.9 → 96 bags. Brick mortar is often quoted per thousand: at 35 a bag that is about 29 bags per thousand before waste, 31 with it.

What went wrong?

Quick referencefor mortar

Sacs: (units × (1 + waste)) ÷ units per bag, rounded up
This page's defaults: block 13 a bag · brick 35 a bag — the supplier's figure for your joint beats both
Per 100 block, 10% waste: about 8.5 bags at 13 a bag
Per 1,000 brick, 10% waste: about 31 bags at 35 a bag
Joint size: a ½ in joint uses about a third more than a ⅜ in — drop the yield, not the waste
Métrique: 25 kg bag ≈ 8 block or 22 brick at this page's defaults
Per 100 block in 25 kg bags, 10% waste: about 14 bags at 8 a bag
Bag weights: 80 lb = 36,3 kg · 25 kg = 55 lb

Waste & overagewhat to add, and why

Masons add 10% to a mortar count because a mix that goes off on the board is thrown away, and a wet day thins it; the waste field starts there.
Bags of mortar come on pallets — if the count is close to a pallet, buy the pallet and skip the last-minute run for two bags.

Mistakes to catchbefore you order

Using the units-per-bag figure for block when laying brick, or the reverse — brick takes far more bags per thousand units, and the toggle changes the default.
Not adjusting the units-per-bag for a thicker joint: a ½ in joint uses a third more mortar than a ⅜ in one for the same wall.
Forgetting the bags for the bed joint under the first course — it takes more mortar than a typical course.

What an inspector looks forthe building inspector, at the masonry review

On this part of the job

The mortar type on the bag against the type the drawing specifies — a stronger mortar is not automatically a better one, and substitutions get questioned.
Joints filled and tooled, head joints as well as beds, and the tooling consistent across the elevation.
How mortar is being batched and retempered. Mud that has sat too long or been watered back repeatedly is a durability item.
Cold- or hot-weather practice if the temperature calls for it: what is being done to protect fresh work, not just that somebody knows it should be.

Have this ready

The specified mortar type, and bags on site that match it.
A consistent batching measure — a shovel count is not one.
Protection materials already on site before the weather calls for them.

Every figure an inspector measures against comes from the code your jurisdiction has adopted, the stamped drawing, or the manufacturer's printed instructions — so none of them are printed here. Look the number up in your own book, type it into the tool, and the arithmetic is yours.

La formule

bags = (units × (1 + waste)) ÷ units per bag, rounded up

The unit count comes from your block or brick tally; the units-per-bag figure is how far one bag stretches with your joint. Dividing gives a fractional bag count, the waste factor absorbs droppings and a stiffened board, and rounding up leaves you with whole bags to carry.

What this tool assumes

Only the yield you type, which is why the tool asks for it rather than guessing. Bag size, material, yield and waste are all set on the page, so nothing about your mortar is fixed behind the scenes.

Questions

How many bags of mortar do I need?: Divide your block or brick count by how many one bag lays, then round up. A bag of mortar mix lays roughly a dozen standard blocks or around thirty-odd bricks, though both depend on the bag size and the joint. Enter your count and the units-per-bag figure above and the bag tally, with a little waste, appears at once.
How many blocks does a bag of mortar lay?: For a typical 80 lb bag of mortar mix, on the order of twelve to fourteen standard blocks with a normal joint — a smaller metric bag lays fewer. It is the editable default here rather than a fixed figure, because a wider joint, a rougher block or a leaner mix all change it. Set it to what your supplier quotes.
Does the joint size matter?: A great deal. A thicker bed and head joint uses more mortar per unit, so fewer units come off each bag. That is exactly why the units-per-bag figure is a field you set rather than a number baked in — dial it down for a fat joint, up for a tight one, and the bag count follows.
Should I round bags up?: Always, and the tool does. You buy whole bags, running out mid-course means a cold joint, and mixing a fresh bag late in the day is a nuisance. A spare bag on the pallet is cheap insurance against stopping the wall short of the top.

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