Mortar Calculator
This mortar calculator estimates how much portland cement and sand to buy when you mix mortar yourself: for stucco and render coats, a mortar bed or screed, or the joints of a brick or block wall. Enter the area, the thickness and the cement-to-sand ratio by volume. You get the number of 94-lb bags, the sand in cubic feet and pounds, and the mortar volume including waste.
Updated
Results
- CementTotal weight
- Sand (volume)Dry, loose
- Sand (weight)At 1,600 kg/m³ (about 100 lb/ft³)
- Mortar volumeIncluding waste
- Dry material volumeCement + sand before mixing
Results are estimates. See the methodology below.
How to use the mortar calculator
- Leave imperial selected (switch to metric for m² and cm).
- Pick the application: stucco / plaster, mortar bed / screed or masonry joints.
- Enter the area in square feet. For walls, length × height minus large openings.
- Enter the thickness in inches. For stucco and screed it is the coat or bed thickness. For masonry it is an average thickness: the mortar volume per square foot of wall. If you know the cubic feet of mortar per 100 sq ft of wall, multiply by 0.12 to get inches.
- Choose the ratio, from 1:2 to 1:6 (one part cement to N parts sand).
- Check the bag weight: 94 lb is the standard full bag of portland cement.
- Under Advanced options, adjust waste (10%) and the dry volume factor (1.30).
How the calculation works
- Mortar volume = area × thickness × (1 + waste)
- Dry volume = mortar volume × dry factor
- Cement = dry volume × 1 ÷ (1 + N), at a bulk density of 1,440 kg/m³
- Sand = dry volume × N ÷ (1 + N), at 1,600 kg/m³ for the weight
- Bags = cement weight ÷ bag weight, rounded up
The dry factor exists because the mix shrinks: cement fills the voids between sand grains, so you need more loose material than finished mortar. The default of 1.30 is the calculator's assumption and you can change it. The bulk densities (1,440 kg/m³ for cement, 1,600 kg/m³ for dry sand) are typical approximations; real sand varies with moisture and grading. Results are shown in pounds and cubic feet; 27 cubic feet make one cubic yard.
One cubic yard of mortar by ratio
| Ratio | Cement | 94-lb bags | Sand |
|---|---|---|---|
| 1:2 | 1,052 lb | 12 | 23.40 ft³ |
| 1:3 | 789 lb | 9 | 26.33 ft³ |
| 1:4 | 631 lb | 7 | 28.08 ft³ |
| 1:5 | 526 lb | 6 | 29.25 ft³ |
| 1:6 | 451 lb | 5 | 30.09 ft³ |
No waste included. The calculator covers cement and sand only; hydrated lime is not counted.
Examples
Stucco coat: 200 sq ft at 3/4 in, ratio 1:3
With 10% waste you need 13.75 ft³ of mortar: 5 bags of portland cement (402 lb) and 13.41 ft³ of sand (about 1,339 lb). Without waste it is 4 bags and 12.19 ft³.
Mortar bed: 120 sq ft at 2 in, ratio 1:4
22 ft³ of mortar with waste: 6 bags (514 lb of cement) and 22.88 ft³ of sand (2,285 lb), a little under one cubic yard.
Block wall joints: 100 sq ft, average 1/2 in, ratio 1:4
4.58 ft³ of mortar with waste: 2 bags (107 lb) and 4.77 ft³ of sand.
Choosing a mix
Masonry mortar in the US is specified under ASTM C270, which covers mortar types by proportion or by property. Quikrete's portland cement data sheet gives volume proportions that include hydrated lime: Type S is 1 part cement, 1/2 part lime and 3-1/2 to 4-1/2 parts masonry sand; Type N is 1 part cement, 1 part lime and 4-3/4 to 5-3/4 parts sand. For stucco scratch and brown coats it lists ASTM C926 Blend I: 1 part cement, 1/2 part lime and 4-1/2 to 6 parts plaster sand.
For these mixes, pick the ratio closest to the sand parts and buy the lime separately. If you use a premixed mortar mix bag, follow the yield printed on the bag instead. For footings, slabs and posts, use the concrete calculator.
Frequently asked questions
How many bags of cement per cubic yard of mortar?
At 1:3 the calculator gives 789 lb, or 9 bags of 94 lb; at 1:4 it is 631 lb, or 7 bags. Add your waste allowance on top.
What is the mortar ratio for stucco?
Quikrete lists ASTM C926 Blend I for scratch and brown coats: 1 part portland cement, 1/2 part hydrated lime, 4-1/2 to 6 parts plaster sand. Follow your plans and local code.
Type S or Type N mortar?
In Quikrete's proportions, Type S uses less lime and less sand per part of cement than Type N. Which type a wall needs is set by ASTM C270, your project specifications and local code, not by this calculator.
What is the dry volume factor?
It is how much loose material you need for one unit of finished mortar. The default 1.30 is an assumption for dry sand; raise it if you measure damp, fluffed-up sand.
Does it include water and lime?
No. Add water gradually until the mortar is workable, and buy lime separately for cement-lime mixes such as Type S or Type N.
How much does the sand weigh?
The calculator also shows sand weight in pounds at 1,600 kg/m³. In the stucco example that is about 1,339 lb; damp sand from a yard weighs more.
Sources
This calculator gives a material estimate based on typical densities and factors. Check mix proportions against your plans, local code and the manufacturer's instructions.