Mortar Mix Calculator

Enter the number of units, assumed mortar volume per 100 units and the actual mix yield per bag. The example 3 ft³ per 100 units and 0.6 ft³ per bag are editable assumptions, not universal manufacturer yields. Joint geometry, unit type and waste need a product- and layout-specific estimate.

Mortar type matters: type N, S and M suit different loads and exposures, and the wrong type can fail. Waste from droppings and loss on the mixer is significant. Hot, dry or cold weather changes the working time and curing.

Structural masonry should follow the design specifications.

Mortar volume needed (cu ft) from brick or block count

Brick or block count	500
Mortar per 100 units	3
Bag yield	0.6
Mortar volume needed (cu ft)	15
Mortar bags needed	25

Common error: Buying to the exact count. Mortar dropped, wasted and left over is unavoidable, and running short in the middle of a course forces a cold joint.

Mortar Mix: formula

Mortar volume = units ÷ 100 × mortar-per-100 units; bags = volume ÷ bag yield

ICC: International Building Code

Mortar Mix: changing Brick or block count

Mortar volume needed (cu ft): assumed Brick or block count scenarios.
Brick or block count	Mortar volume needed (cu ft)	Mortar bags needed
400	12	20
450	13.5	22.5
500 (example)	15	25
550	16.5	27.5
600	18	30

Mortar Mix: compare input ranges

Mortar Mix Calculator: Mortar volume needed (cu ft) with each input moved on its own, every other input held at the worked-example value.
Input	Tested from	To	Mortar volume needed (cu ft): low input	Mortar volume needed (cu ft): high input	Swing
Brick or block count	450	550	13.5	16.5	3 (20%)
Mortar per 100 units	2.7	3.3	13.5	16.5	3 (20%)
Bag yield	0.54	0.66	15	15	0

Mortar Mix: individual input comparisons

Mortar Mix Calculator: change one input at a time; other values remain at the stated example.
Input	Value	Mortar volume needed (cu ft)	Mortar bags needed
Brick or block count	400	12	20
	450	13.5	22.5
	500	15	25
	550	16.5	27.5
	600	18	30
Mortar per 100 units	2.4	12	20
	2.7	13.5	22.5
	3	15	25
	3.3	16.5	27.5
	3.6	18	30
Bag yield	0.48	15	31.3
	0.54	15	27.8
	0.6	15	25
	0.66	15	22.7
	0.72	15	20.8

Mortar volume needed (cu ft): Brick or block count against Mortar per 100 units

Mortar Mix: Mortar volume needed (cu ft) at combined Brick or block count and Mortar per 100 units settings.
Brick or block count / Mortar per 100 units	2.4	3	3.6
400	9.6	12	14.4
450	10.8	13.5	16.2
500	12	15	18
550	13.2	16.5	19.8
600	14.4	18	21.6

Mortar Mix: values and definitions

Worked-example inputs and the results they produce for the Mortar Mix Calculator.
Quantity and definition	Value used
Brick or block count — Total number of bricks or blocks being laid.	500
Mortar per 100 units — Cubic feet of mortar typically needed per 100 units at your joint thickness (about 3 for standard brick with a 3/8-inch joint).	3
Bag yield — Mixed cubic-foot yield of one bag of mortar mix.	0.6
Mortar volume needed (cu ft)	15
Mortar bags needed	25

Brick or block count: half and double

Mortar Mix scale comparison; assumed inputs.
Brick or block count	Mortar volume needed (cu ft)
250	7.5
500	15
1,000	30

Mortar is estimated from the count of units, and the joint size drives the quantity. At about 3 cubic feet per hundred units, 500 bricks or blocks need about 15 cubic feet, and with a bag that yields 0.6 cubic feet that is about 25 bags. Wider joints and rougher units use more, and waste on the board and in the mixer adds to it.

Mix only what you can use before it stiffens, since mortar cannot be reworked much after it starts to set.

Check the yield on the bag and the mortar-per-hundred figure for your unit size and joint width. A larger unit uses less mortar per square foot of wall.

Count the blocks on the CMU block calculator, estimate concrete on the concrete volume page, and footings on the footing size calculator. The paver and cubic feet pages cover related volumes, and the rebar page covers reinforcement.

Does an 80-pound bag always have the same usable yield?

No. Use the yield printed for the actual product and mixing instructions. Bag weight alone does not specify mixed volume.

Can the same per-unit volume be used for every wall?

No. Unit dimensions, hollow or solid construction, joint thickness and laying method change mortar demand.

Mortar Mix Calculator