Masons use about 7–8 ft³ of mortar per 1,000 modular bricks and about 8½ ft³ per 100 standard blocks with ⅜ in joints. Premixed mortar comes in 60–80 lb bags; on larger jobs it is cheaper to mix Portland cement, hydrated lime and masonry sand. Type S is the usual choice below grade and for structural walls, Type N for general above-grade work.
How to use the Mortar Calculator
- Masonry unit
- Number of units
- Waste
- Mortar type (cement : lime : sand)
- Premix bag
- Price per bag of premix
- Every result field is editable: type into Mortar volume and Number of units plus every other field update to match.
Results update as you type, and every field accepts the units shown in its menu.
How it works
Choose the masonry unit, enter how many you will lay, the waste allowance, the mortar type and bag size. The calculator multiplies by the mortar per unit, then splits the volume into bags of premix and into cement, lime and sand for a site mix.
Mortar types
| Type | Proportions | Min. strength | Use |
|---|---|---|---|
| M | 1 : ¼ : 3 | 2,500 psi | Below grade, heavy loads |
| S | 1 : ½ : 4½ | 1,800 psi | Foundations, retaining walls, structural |
| N | 1 : 1 : 6 | 750 psi | Above-grade walls, veneer |
| O | 1 : 2 : 9 | 350 psi | Interior, non-load-bearing, repointing |
Tips for an accurate estimate
- Measure the formwork, not the drawing – forms bulge and subgrades are rarely perfectly flat, so add 5–10%.
- Below about 1 cubic yard, premixed bags are usually cheaper; above that, ready-mix saves time and gives a more consistent pour.
- Order ready-mix in quarter- or half-yard steps and ask about short-load fees for small deliveries.
- Keep fresh concrete damp for at least a week – curing matters as much as the mix for final strength.
Common mistakes to avoid
- Running short mid-pour, which leaves a weak cold joint.
- Adding extra water on site to make concrete easier to place – it lowers strength and increases cracking.
- Ignoring the volume of rebar, posts or pipes in the pour, or the gravel base under it.
Inputs explained
| Field | What to enter |
|---|---|
| Masonry unit | Choose one: Modular brick (≈ 0.008 ft³ each), Standard / king brick (≈ 0.009 ft³), UK brick 215 × 65 (≈ 0.5 L), 8 in concrete block (≈ 0.085 ft³) … |
| Number of units | A number |
| Waste | In % |
| Mortar type (cement : lime : sand) | Choose one: Type M – 1 : ¼ : 3, Type S – 1 : ½ : 4½, Type N – 1 : 1 : 6, Type O – 1 : 2 : 9 |
| Premix bag | Choose one: 80 lb (≈ 0.67 ft³), 60 lb (≈ 0.50 ft³), 40 lb (≈ 0.33 ft³), 25 kg (≈ 0.013 m³) … |
| Price per bag of premix | Units: /piece |
What each result means
- Mortar volume = [Number of units]×[Masonry unit]×(1 + [Waste]÷100)
- Bags of premixed mortar = ceil([Mortar volume]÷[Premix bag])
- Premix cost = [Bags of premixed mortar]×[Price per bag of premix]
- Site mix: Portland cement (94 lb bags) = ceil([Mortar volume]÷[Sand parts]÷0.028316846592)
- Site mix: hydrated lime = [Mortar volume]×[Lime parts]÷[Sand parts]
- Site mix: masonry sand = [Mortar volume]
Formula
Mortar = units × mortar per unit × (1 + waste)Site mix by volume: cement : lime : sand (Type S = 1 : ½ : 4½)Cement (ft³ ≈ 94 lb bag) = mortar ÷ sand partsWorked example
Inputs — Masonry unit: Modular brick (≈ 0.008 ft³ each); Number of units: 1,000; Waste: 15 %; Mortar type (cement : lime : sand): Type S – 1 : ½ : 4½; Premix bag: 80 lb (≈ 0.67 ft³); Price per bag of premix: $9 /piece.
Results — Mortar volume = 9.2 ft³; Bags of premixed mortar = 14; Premix cost = $126.00; Site mix: Portland cement (94 lb bags) = 3; Site mix: hydrated lime = 1.02 ft³; Site mix: masonry sand = 9.2 ft³.
Frequently asked questions
How much mortar per 1,000 bricks?
About 7–8 ft³ for modular brick with ⅜ in joints – roughly 10–12 bags of 80 lb premix.
How many blocks does a bag of mortar lay?
An 80 lb bag lays about 12–13 standard 8 in blocks.
What is the difference between Type S and Type N mortar?
Type S is stronger (1,800 psi) for foundations and retaining walls; Type N (750 psi) is softer and suits above-grade veneer and interior walls.
Why does the sand equal the mortar volume?
The cement and lime paste fills the voids between sand grains, so the finished mortar takes up about the same volume as the dry sand.
What formula does the Mortar Calculator use?
Mortar = units × mortar per unit × (1 + waste).