Cubic feet
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Monolithic Slab Calculator
Monolithic Slab calculator
Calculate concrete for a thickened-edge (monolithic) slab. Cubic yards, bags, ready-mix loads and weight — with a waste margin built in, nothing leaves your browser.
Dimensions
FIG. 01Volume ÷ 27 = cubic yards. Pros order to the nearest ½ yard and add a waste margin — running short mid-pour risks a cold joint.
You need
—cu yd
Order to nearest ½ yd → — · —
Cubic meters
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80 lb bags
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60 lb bags
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Est. weight
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Best buy
see above
How this is calculated
A monolithic (thickened-edge) slab pours the floor and its perimeter footing in one shot — the edges drop down into a deeper beam that carries the wall load. It's common for sheds, garages and homes on grade.
cubic yards = volume in cubic feet ÷ 27 × (1 + waste%)
For the full method and sources, see the methodology page. Comparing buying options? Use the bags-vs-ready-mix calculator.
FAQ
What is a monolithic slab?
A monolithic (thickened-edge) slab pours the floor and its perimeter footing in one shot — the edges drop down into a deeper beam that carries the wall load. It's common for sheds, garages and homes on grade.
How do I calculate concrete for a monolithic slab?
Add the flat slab body (length × width × thickness) to the extra concrete in the perimeter beam (perimeter × beam width × the depth below the slab). This calculator handles both — set the beam depth deeper than the slab to see the edge volume.