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Mortar Calculator

A mortar calculator tells you how many bags of mortar mix to buy for the blocks or bricks you are laying. Pick block or brick, enter the count, and it does the rest — handy once a block or brick calculator has given you the unit count.

Your measurements

Result

Mortar is the easy thing to under-buy. Bags are cheap and they ship, so round up and keep a spare.

How it is calculated

With standard 3/8 in joints and 80 lb bags, mortar covers roughly 33 concrete blocks or 35 bricks per bag. The calculator divides your unit count by that and rounds up. Pre-mixed mortar already contains sand; mason's mix needs separate masonry sand.

Steps

Choose whether you are laying concrete blocks or bricks.
Enter the number of units.
Read the number of 80 lb mortar bags.
Buy a little extra — mortar sets fast once mixed.
Add masonry sand if your mix needs it.

Worked example

Laying 300 concrete blocks needs about 10 bags of mortar; 300 bricks need about 9 bags.

Common questions

How many blocks does a bag of mortar lay?

About 33 standard blocks per 80 lb bag with normal joints. Bricks are similar at about 35 per bag.

What mortar type do I need?

Type N for most above-grade walls, Type S for higher-strength or below-grade. Check your spec and the bag.

Do I need sand too?

Pre-mixed mortar mix already contains sand. Straight masonry cement needs separate masonry sand.

How much should I mix at once?

Only what you can use in about an hour — it stiffens as it cures and cannot be re-tempered indefinitely.