Concrete & Masonry Calculators
Concrete & Masonry Calculators for slabs, footings, columns, and block walls. Estimate yards, bags, bricks, rebar, mortar, and grout. Then check mix ratios, batch yield, and form pressure before you pour.
What Concrete & Masonry Calculators Cover
Concrete and masonry jobs fail on quantities more than on technique. A short pour leaves a cold joint. A short block order stops the wall halfway. The tools above turn your measurements into order amounts before you buy.
They fall into five groups. Each group matches a stage of the job.
Pour Volume
Start here for anything you fill with concrete. The Concrete Calculator handles slabs, footings, and round holes. The Concrete Footing Calculator and Trapezoidal Footing Volume Calculator cover footings with straight or sloped sides.
For round shapes, use the Sonotube Calculator, Concrete Column Calculator, or Round Hole Volume Calculator. Steps and landings go in the Concrete Stairs Calculator. The Concrete Slope Calculator sets the fall so a slab drains.
Mix, Bags, and Batch Checks
Once you know the volume, these tools break it down. The Concrete Mix Calculator and Cement Calculator split it into cement, sand, gravel, and water. The Water To Cement Ratio Calculator checks how much water the mix gets.
After a batch arrives, the Concrete Yield Calculator compares what you received with what you ordered. The Concrete Density Calculator finds unit weight from mass and volume.
Block and Brick Walls
The Concrete Block Calculator counts CMU for a wall. The Concrete Block Fill Calculator and CMU Grout Calculator estimate what goes into the cores. The Grout Mix Ratio Calculator sets the grout batch.
For brick, the Brick Calculator gives a wall count. The Brick Circle Calculator handles round patios and rings. The Brick Course Height Calculator checks how courses line up with a target height. The Mortar Calculator covers the bags for both brick and block.
Reinforcement and Retaining Walls
The Rebar Calculator plans bar spacing, count, and steel weight. The Retaining Wall Calculator estimates blocks and capstones. The Retaining Wall Slope Calculator works out the wall’s setback and lean.
Two tools deal with how concrete behaves. The Concrete Pressure Calculator finds the push of fresh concrete on formwork. The Concrete Shrinkage Calculator estimates length change as it dries.
Surface Prep
The Self Leveling Coverage Calculator estimates bags of underlayment from area and depth. The Tile Mortar Calculator estimates thinset for tile set on a slab.
Quick Reference Numbers
These are the rates most estimators start from. Bag yields come from Quikrete and Sakrete product data sheets. The brick rate comes from BIA Technical Note 10.
| Item | Rate | Per cubic yard or unit |
|---|---|---|
| 80 lb concrete bag | 0.60 cu ft | 45 bags per cu yd |
| 60 lb concrete bag | 0.45 cu ft | 60 bags per cu yd |
| 40 lb concrete bag | 0.30 cu ft | 90 bags per cu yd |
| 8 × 8 × 16 concrete block | 1.125 per sq ft | 113 per 100 sq ft |
| Modular brick, 3/8 in joint | 6.75 per sq ft | 675 per 100 sq ft |
One cubic yard is 27 cubic feet. That is why the bag counts above are 27 divided by the bag yield.
Mortar yield varies by brand and joint size. Use the yield printed on the bag you plan to buy.
Worked Example: A 10 × 10 Slab
Take a 10 ft by 10 ft patio slab poured 4 inches thick. Convert the depth to feet first. Four inches is 0.333 ft.
Volume is 10 × 10 × 0.333, which is 33.3 cubic feet. Divide by 27 to get 1.23 cubic yards.
In 80 lb bags, that is 33.3 ÷ 0.60, or about 56 bags before waste. Add 5% and you need 59 bags.
Bags or Ready-Mix?
Bag count is a quick way to decide. One cubic yard already takes 45 bags of 80 lb mix. That is 3,600 lb of dry material to lift and mix by hand.
Many estimators treat about one cubic yard as the crossover point. Below it, bags are usually simpler. Above it, a ready-mix truck often costs less per yard and gives a more even pour. Suppliers often add a short-load fee for small orders, so ask for a quote at your volume.
How Much Waste to Add
Geometric volume is never the full order. Subgrades are rarely flat. Forms bow. Some mix stays in the mixer.
A 5% allowance suits a simple slab or a straight wall. Walls with many corners, cuts, or openings often need 10% or more. For brick, BIA guidance adds at least 5% to net quantities.
Subtract door and window openings before you apply a waste factor. Waste should cover breakage and cuts, not wall area you won’t build.
Common Measuring Mistakes
Mixing units. Length in feet and depth in inches cannot be multiplied together directly. Convert everything to feet first.
Treating round shapes as squares. A square drawn around a circle holds about 27% more volume. Use a round-shape tool for tubes, columns, and holes.
Using actual block size for layout. An 8 × 8 × 16 block is really about 7-5/8 × 7-5/8 × 15-5/8 inches. The nominal size includes the mortar joint, and course counts depend on it.
FAQs
How many 80 lb bags of concrete make a cubic yard?
About 45 bags. Each 80 lb bag yields about 0.60 cubic feet, and a cubic yard is 27 cubic feet. Add a few bags for waste.
How many concrete blocks are in a square foot?
About 1.125 standard 8 × 8 × 16 blocks. Each block with its mortar joint covers 8 × 16 inches, or 128 square inches. A square foot is 144 square inches.
How many bricks per square foot of wall?
About 6.75 modular bricks with a 3/8 inch joint, per BIA Technical Note 10. Larger brick sizes need fewer per square foot. A double-wythe wall needs about twice as many.
Should I measure openings out of a wall?
Yes. Subtract doors and windows to get net wall area. Then apply the block or brick rate and your waste factor.
Are these results good enough for structural work?
They are for planning and ordering. Footing size, rebar layout, and retaining wall design depend on loads, soil, and local code. Have those confirmed by an engineer or your building department.