Mortar counted from the joints themselves, not a rule of thumb. Enter how many blocks or bricks you are laying for the true mortar volume and the 60 lb and 80 lb bag counts.
Mortar Calculator
Method: bed + head joint volume per unit, from joint dimensions, face-shell bedding for block, full bedding for brick. Premix yields used: 0.45 ft³ per 60 lb bag, 0.60 ft³ per 80 lb bag.
You need
Full-bedding block work (solid units, or cores grouted at the joint) uses more mortar, switch the waste to 30% or use the brick bedding figure as a closer proxy, and confirm against your mason’s own rate after the first day.
A mortar calculator adds up the bed and head joints: an 8 in block laid face-shell uses about 0.0134 ft³ of mortar per block, a modular brick about 0.0081 ft³. Five hundred blocks therefore need 6.7 ft³ of mortar, 18 × 60 lb bags with a 15% waste allowance. Enter your unit count above.
How to Calculate Mortar for Block and Brick
Most mortar guides quote a single ‘bags per hundred’ figure with no visible method, which is why they disagree with each other. Mortar use is not mysterious: it is the volume of the joints, and joints are geometry, a bed joint and a head joint per unit, at a known thickness and bedding width. This mortar calculator works from that geometry, states its premix yields, and adds an honest waste allowance for droppings and board losses.
The Formula
Mortar per modular brick ≈ 0.0081 ft³ (full bedding, 3/8 in)
Bags = total ft³ × (1 + waste %) ÷ yield, 0.45 ft³ per 60 lb bag · 0.60 ft³ per 80 lb bag
The block figure assumes face-shell bedding, mortar on the two face shells only, which is standard for hollow block. Solid bedding, deeper joints or heavily tooled joints all raise the per-unit volume; the waste field is where masons tune this calculator to their own crew’s real rate.
Worked Example: 500 Blocks (a 20 × 8 ft Wall, Plus Spares)
Mortar volume = 500 × 0.0134 = 6.70 ft³. With 15% for droppings and board waste: 7.71 ft³. Bags: 7.71 ÷ 0.45 = 17.1 → 18 × 60 lb bags, or ÷ 0.60 = 13 × 80 lb bags. Cross-check against the field rate (about 3 bags per 100 blocks for site-batched masonry cement systems), different systems, similar totals; the geometry is the common ground.
Mortar per 100 Units: Quick Rates
| Work | Mortar volume | 60 lb bags | 80 lb bags |
|---|---|---|---|
| 100 blocks, face-shell | 1.34 ft³ | 3 | 3 |
| 100 blocks, with 15% waste | 1.54 ft³ | 4 | 3 |
| 1,000 modular bricks | 8.06 ft³ | 18 | 14 |
| 1,000 bricks, with 15% waste | 9.27 ft³ | 21 | 16 |
| 100 sq ft of 8 in block wall (= 113 blocks) | 1.51 ft³ | 4 | 3 |
Rates exclude grout for filled cells (that is the CMU Calculator’s job) and assume 3/8 in joints. Historic repointing, rubble work and stone use far more mortar per unit, those are different systems and this page’s geometry does not pretend to cover them.
Why Mortar Waste Runs at 15%
Mortar falls off the board, skins over in the tub, gets tooled out of joints and is discarded at every batch’s end of life, and its working life is about 2½ hours, after which retempering has limits. Fifteen percent is a fair premix allowance for block work in normal weather; hot windy days (faster board loss) argue for 20% and smaller batches, not for wetter mixes.
How to Measure and Calculate: Step by Step
- Count the units to be laid (blocks from the Block Calculator, bricks from your take-off).
- Select the unit type so the right joint geometry applies.
- Set waste at 15% (20% in hot, windy conditions).
- Enter the count above; choose 60 lb or 80 lb bags by the result.
- After day one, compare actual bag use per 100 units and tune the waste for the rest of the job.
Worked Example 2: 3,000 Modular Bricks for a Veneer
Mortar = 3,000 × 0.00806 = 24.2 ft³; with 15%: 27.8 ft³ → 62 × 60 lb bags or 47 × 80 lb bags. Veneer work wastes more at openings and ties; if the wall is cut up with windows, hold the 15% and stage the bags by elevation so a shortage shows up on paper before it shows up on the scaffold.
Common Quantities at a Glance: Cheat Sheet
| Job / quantity | Result |
|---|---|
| Per 100 blocks | ≈ 1.54 ft³ · 4 × 60 lb bags (with waste) |
| Per 1,000 bricks | ≈ 9.27 ft³ · 21 × 60 lb bags (with waste) |
| One 60 lb bag | 0.45 ft³ · lays ≈ 29 blocks |
| One 80 lb bag | 0.60 ft³ · lays ≈ 39 blocks |
| Joint thickness effect | 1/2 in joints use ≈ 33% more than 3/8 in |
| Mortar working life | ≈ 2.5 hours per batch |
Practical Tips From the Job
Batch size is a quality decision: mix what the crew places in an hour, keep the board shaded and damp in summer, and never resurrect a stiffened batch with extra water beyond a single retemper. Keep one unopened bag per hundred units beyond the count as the site spare, mortar is the cheapest material on the job to have and the most expensive to run out of at 4 pm.
Common Mistakes to Avoid
- Trusting a single bags-per-hundred figure with no stated method.
- Using the block rate for full-bedded solid units.
- Ordering for the exact unit count with no droppings allowance.
- Mixing huge batches that outlive their working life.
- Confusing mortar bags with grout volume for filled cells.
What It Costs and How to Order Smart
Mortar is a small line item, but it carries weight: the example’s 18 bags are a modest shelf total, yet a mortar shortage idles a whole masonry crew. Price 60 lb versus 80 lb bags per cubic foot of yield, not per bag, the 80 lb bag carries about a third more mortar and usually wins on price wherever the crew can handle the weight. Site-batched masonry cement and sand beats both on big walls; the geometry on this page still sets the volume to batch.
Who Uses This Calculator?
Builders estimating masonry packages use the per-100 rates for fast budgets. Contractors order from the bag counts and tune waste from day-one actuals. Engineers rarely count mortar but do specify its type, N, S or M, which this page’s yields sit behind. Architects checking a veneer quantity use the brick rate, and homeowners repointing or building a first block wall get a method they can verify, not just a number.
Mortar Calculator FAQs
How many bags of mortar do I need for 500 blocks?
From the joint geometry: 500 blocks × 0.0134 ft³ = 6.7 ft³ of mortar, 7.71 ft³ with a 15% allowance. That is 18 × 60 lb premix bags (0.45 ft³ each) or 13 × 80 lb bags (0.60 ft³ each). If your crew’s actual rate differs after day one, adjust the waste percentage, the geometry will not change.
How much mortar is needed per 100 blocks?
About 1.34 ft³ of placed mortar per 100 standard blocks with face-shell bedding and 3/8 in joints, 1.54 ft³ with a normal waste allowance, roughly 3–4 × 60 lb premix bags. Site-mixed systems quote differently (about 3 bags of masonry cement per 100 blocks, plus sand) because the bag is an ingredient there, not the finished mortar.
How many bags of mortar for 1,000 bricks?
Modular brick at full bedding uses about 0.0081 ft³ per brick: 1,000 bricks need 8.06 ft³, or 9.27 ft³ with 15% waste, about 21 × 60 lb bags or 16 × 80 lb bags. Larger brick formats use less mortar per thousand (fewer joints), small handmade bricks more; the joint count is what you are really counting.
What is the yield of a 60 lb bag of mortar mix?
About 0.45 ft³ of mixed, placed mortar for standard premix, the figure used here and printed by major manufacturers. An 80 lb bag yields about 0.60 ft³. Yield is where bag comparisons live: a cheaper bag with a lower yield is not cheaper per joint, so always divide price by the yield before judging.
What is the difference between Type N and Type S mortar?
Strength and use. Type N (about 750 psi) is the general above-grade choice, veneers, chimneys, interior work. Type S (about 1,800 psi) adds strength and bond for below-grade, retaining and load-bearing masonry. Type M is stronger still. The calculator’s volumes are identical for all three; the type comes from the spec, and stronger is not automatically better, mortar should not be harder than the unit it joins.
Does joint thickness change mortar quantity much?
Directly and proportionally: joints at 1/2 in instead of the standard 3/8 in use about a third more mortar across the whole wall. Rubble and historic work with fat joints can double the standard rates. If your joints are non-standard, scale the per-unit figures by (your joint ÷ 3/8) as a first correction.
Can I use concrete mix instead of mortar?
No, concrete’s coarse aggregate will not fit a 3/8 in joint, and the mixes are designed for opposite jobs. Mortar is a workable, water-retentive bonding material; grout is the fluid fill for block cores; concrete is the structural fill. Three materials, three bags, and using the wrong one shows up as weak joints or unfilled cells.
How long is mixed mortar usable?
About 2½ hours in normal conditions, less in heat. Board life is why batch size matters and part of where the 15% waste allowance goes, the last of a big batch is often discarded. Retemper once with minimal water if it stiffens early; mortar that has begun to set goes in the bin, not the wall.
How accurate is this mortar calculator?
The joint geometry is standard and stated openly, which makes the result auditable, change any assumption (yield, joint, bedding) and the effect is visible. Crew technique moves real usage by ±10–15%, which the waste field absorbs. For production work, calibrate with one day of actuals and the calculator becomes a forecasting tool, not just an estimate.
Related Calculators
Sources used for standards and conversions: National Ready Mixed Concrete Association (NRMCA) guidance on ordering and yield; American Concrete Institute (ACI) practice for mix and placement; Portland Cement Association (PCA) design and control guidance; US manufacturers’ printed yields (80 lb bag = 0.60 ft³). Depths, sizes and spacings set by your local building code govern wherever they differ from the general figures here.
Disclaimer: Results are estimates for planning and ordering. Before ordering, confirm the quantities with your supplier. Structural work (footings, walls, columns, beams and anything load-bearing) should be checked by a licensed engineer.