Construction & Materials
Concrete Slab Calculator
Use this concrete slab calculator for patios, shed pads, sidewalks, garage aprons, and other rectangular pours.
Estimated quantity
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- Volume with waste
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- Cubic yards
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- Estimated material cost
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Student quick launch
Grade planning, algebra checks, and formulas students reach for most.
Study path
Use this calculator with
Follow these when you want the formula behind the answer, a short lesson, or nearby tools in the same topic.
What the concrete slab calculator solves
Use this concrete slab calculator for patios, shed pads, sidewalks, garage aprons, and other rectangular pours.
Formula
How to use it
- Enter length and width in feet.
- Enter depth or thickness in inches.
- Use the package yield or truckload yield to round up material.
How to read the answer
The bag count is rounded up after adding waste because concrete is hard to stretch once the pour starts.
Common mistakes and edge cases
- Convert slab thickness from inches to feet.
- Add more waste for uneven subgrade or complex forms.
- Check whether ready-mix delivery is more practical for larger pours.
Worked examples
Small patio slab
Estimated quantity
74 bags
Thicker shed pad
Estimated quantity
75 bags
Frequently asked questions
Why show both cubic feet and cubic yards?+
Bags often list cubic-foot yield, while bulk concrete, soil, mulch, and aggregate are commonly ordered in cubic yards.
Does this replace a contractor estimate?+
No. It is a planning calculator. Site conditions, compaction, forms, slopes, and local material packaging can change the order quantity.
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Last updated: May 15, 2026