Concrete Mix and Mortar Calculator
Enter your volume and a mix ratio, and this concrete mix and mortar calculator returns the cement, sand and aggregate you need, or the number of mortar bags for a block or brick wall. It helps when you are batching your own mix from raw materials instead of buying pre blended bags.
Concrete Mix Calculator
Bagged concrete is one product. A site mix is made from separate cement, sand and stone, and the proportions decide the strength. Mortar is a different material, used to bond block and brick, and it is cement, sand and lime with no coarse stone.
Concrete mix ratios
A mix ratio lists the parts of cement, sand and aggregate by volume. The general purpose ratio is 1:2:3, which gives roughly 22 percent cement, 33 percent sand and 45 percent stone. Leaner mixes use more aggregate for footings and fill; richer mixes use less for higher strength.
| Mix ratio | Rough strength | Common use |
|---|---|---|
| 1:3:6 | Lower | Mass fill, lean base |
| 1:2:3 | Medium | Footings, general flatwork |
| 1:1.5:3 | Higher | Structural slabs and columns |
The water to cement ratio matters as much as the aggregate split. Too much water weakens the mix and causes shrinkage cracks, so add only enough for a workable, plastic consistency.
Worked example, a site mix
You need 1 cubic yard of 1:2:3 concrete, which is 27 cubic feet. Dry materials bulk down when mixed, so builders use a dry volume factor of about 1.54. That gives roughly 41.6 cubic feet of dry material. Split by the ratio parts (1 plus 2 plus 3 is 6 parts): about 6.9 cubic feet of cement, 13.9 of sand and 20.8 of stone. One 94 pound bag of cement is about 1 cubic foot, so you would need around 7 bags of cement for that yard, plus the sand and stone. For most small jobs, bagged concrete is simpler, but a site mix is cheaper at volume.
Mortar for block and brick
Mortar is sold by type under ASTM C270. Type N suits most above grade walls, Type S handles higher loads and below grade work, and Type M is for heavy load and foundations. The amount you need scales with the number of units and the joint size.
| Masonry | Typical mortar need |
|---|---|
| Standard 8 by 8 by 16 block | about 3 bags of 80 lb mortar per 100 block |
| Standard brick | about 1 bag of 80 lb mortar per 100 to 125 brick |
These are planning figures. Waste, joint width and wall layout all shift the real count, so carry 5 to 10 percent extra.
Worked example, a block wall
A wall of 300 standard blocks at about 3 bags of mortar per 100 block needs around 9 bags of 80 pound mortar. Add 10 percent for waste and buy 10. Order the matching sand if you are mixing mortar from cement and lime instead of buying pre blended bags.
Related calculators
- Concrete calculator for the volume you feed into a mix ratio
- Bags calculator for pre blended concrete bags
- How to calculate concrete guide for formulas and strength
Frequently asked questions
What is the best concrete mix ratio?
A 1:2:3 ratio of cement, sand and aggregate suits most general work. Use 1:1.5:3 for higher strength structural pours and a leaner 1:3:6 for fill.
How much cement do I need for a cubic yard of concrete?
For a 1:2:3 site mix, about 7 bags of 94 pound cement per cubic yard, plus the matching sand and stone. Bagged concrete avoids this math.
What is the difference between concrete and mortar?
Concrete contains coarse stone and is used for structural volume. Mortar is cement, sand and lime with no stone, used to bond block and brick.
How many bags of mortar do I need per 100 block?
About 3 bags of 80 pound mortar per 100 standard blocks, before waste. Joint size and layout change this, so add 5 to 10 percent.
What type of mortar should I use?
Type N for most above grade walls, Type S for higher loads and below grade, and Type M for heavy load and foundations, following ASTM C270.
Is a site mix cheaper than bagged concrete?
At volume, yes, since raw cement, sand and stone cost less than pre blended bags. For small jobs, bags are faster and more consistent.
References
- ASTM C270, Standard Specification for Mortar for Unit Masonry: https://www.astm.org/c0270-19ae01.html
- Portland Cement Association, concrete and mortar basics: https://cement.org
- Quikrete, product data sheets for concrete and mortar mixes: https://www.quikrete.com
Methodology: concrete material amounts use the mix ratio with a dry volume factor of about 1.54; mortar counts use typical bags per 100 units. Real amounts vary with water, joint size and waste. Confirm structural mix design with a licensed engineer. Recommended: attribute this page to a named author and add a review date.