Concrete for a slab with perimeter footing
This calculator adds the main slab volume to the extra volume around the perimeter. The 40 ft by 30 ft slab is 1,200 sq ft, with 140 linear ft of perimeter edge.
Why the slab thickness is not double-counted
The total edge depth input is 18 inches, including the 6 inch slab. The formula counts the full slab first, then adds only the extra 12 inches below the slab around the perimeter.
Quantity estimate, not footing design
The calculator does not choose footing width, frost depth, reinforcement, or bearing requirements. Use dimensions from plans, local code guidance, or a qualified professional, then use this page to estimate concrete volume.
When to split the slab into sections
Split the estimate when the edge depth changes, when an apron or porch is poured separately, or when interior grade beams, pier pads, steps, or thickened areas have different dimensions.
Slab with perimeter footing examples
Examples include slab volume plus extra perimeter edge volume before waste. Footing dimensions are planning inputs, not design recommendations.
| Project | Slab and edge inputs | Cubic yards before waste |
|---|---|---|
| 12 ft x 16 ft shed slab | 4 in slab, 1 ft edge width, 10 in total edge depth | 3.41 cu yd |
| 24 ft x 24 ft garage slab | 4 in slab, 1.33 ft edge width, 12 in total edge depth | 10.26 cu yd |
| 30 ft x 40 ft shop slab | 5 in slab, 1.33 ft edge width, 12 in total edge depth | 22.54 cu yd |
| 40 ft x 60 ft barn slab | 5 in slab, 1.33 ft edge width, 12 in total edge depth | 42.78 cu yd |
Before you calculate
- Measure the formed slab length and width in feet.
- Enter the main slab thickness separately from the total perimeter edge depth.
- Use the planned footing or thickened-edge width from drawings, not a guessed structural size.
Common mistakes
- Double-counting the slab thickness inside the perimeter footing volume.
- Using a material calculator to choose footing dimensions or frost depth.
- Forgetting separate pads, interior beams, aprons, steps, or piers that use different dimensions.
Formula
cubic yards = ((length * width * (slabThickness / 12)) + (2 * (length + width) * footingWidth * max(0, footingDepth - slabThickness) / 12)) / 27 * (1 + wastePercent / 100)
Assumptions
- Defaults represent a shop slab with thickened edge footing.
- The footing volume is calculated as the deeper perimeter edge beyond the slab thickness.
- Required footing size, frost depth, reinforcement, and inspection details must come from project requirements.
Example
Estimated concrete needed: 33 cubic yards
How to use this calculator
- Enter length in ft.
- Enter width in ft.
- Enter slab thickness in in.
- Enter footing width in ft.
- Enter total edge depth in in.
- Enter waste in %.
- Review the live estimate and compare it with the example result.
- Check the formula, assumptions, product labels, and site conditions before using the Shop Slab With Footing Calculator result to plan materials.
Before you buy materials
- Use the result as a ready-mix planning number and confirm final rounding with the supplier.
- Verify footing dimensions, reinforcement, base prep, vapor barrier, and inspection requirements before ordering.
FAQ
What is the example shop slab with footing cubic-yard result?
Use length, width, slab thickness, footing width, then calculate the planning result. In the default example, the result is 33 cubic yards.
How do I calculate concrete for a slab with footing?
Calculate the slab volume first, then add the extra perimeter footing volume. Use cubic yards = (slab cubic feet + extra edge cubic feet) / 27, then add waste.
What is a monolithic slab?
In this calculator, a monolithic slab means the slab and thickened perimeter edge are estimated together as one pour. The page estimates quantity only, not structural design.
Why subtract slab thickness from footing depth?
The slab volume is already counted across the whole footprint. Subtracting slab thickness from the total edge depth prevents the edge concrete from being counted twice.
Does this calculator design footing size?
No. It only estimates concrete quantity from dimensions you provide. Required footing size depends on plans, soil, loads, frost depth, and local code.
Should I include waste for a slab with footing?
Yes. A visible waste buffer helps cover excavation variation, form loss, uneven base, and ordering variance. Confirm final rounding with the ready-mix supplier.
Related calculators
This calculator is for planning estimates only. Verify final quantities with product labels, project conditions, and a qualified professional when accuracy matters.