Concrete Slab Calculator – Accurate Estimates for Every Project
This concrete slab calculator helps you estimate how much concrete you'll need for flatwork like patios, footings, shed foundations, garage slabs, and more. Get quick and accurate results in cubic yards and pre-mixed bag estimates based on your project’s dimensions.
How It Works
- Calculates volume in cubic feet
- Converts to cubic yards (used for ready-mix concrete delivery)
- Estimates how many 60 lb and 80 lb concrete bags are required
Just enter the length, width, and depth of your slab and the calculator instantly provides volume totals. Whether you're a DIY homeowner or professional builder, this tool simplifies concrete planning.
Concrete Volume Formula
(Length × Width × Depth in feet) ÷ 27 = Cubic Yards
Cubic Feet ÷ 0.45 = 60 lb bags
Cubic Feet ÷ 0.6 = 80 lb bags
Common Uses for Slab Concrete
- Garage slabs and carports
- Garden sheds and workshops
- Driveways and walkways
- Patios, decks, and outdoor entertaining areas
- Basement floors or foundations
Tips for Accurate Results
- Always measure twice before ordering concrete
- Round up your total slightly to cover waste, spillage, or over-excavation
- Plan for wheelbarrow access or pump trucks if pouring in hard-to-reach areas
- For large slabs, consider adding rebar or mesh reinforcement
FAQs About Concrete Slabs
How deep should my concrete slab be?
Most residential slabs range from 4–6 inches deep. Driveways may require thicker slabs (up to 6–8 inches) for heavy loads.
Should I use pre-mixed bags or order ready-mix concrete?
Pre-mixed bags work for small jobs under 1 yard³. For anything larger, ordering ready-mix is more efficient and cost-effective.
How do I calculate formwork and reinforcement?
This calculator focuses on concrete volume. For formwork, add a few inches around the perimeter. Reinforcement depends on load — consult with a builder or engineer if unsure.
Estimate With Confidence
Get your slab job right the first time. Use this calculator to confidently estimate your concrete needs and avoid shortfalls or over-ordering. Save time, reduce waste, and budget accurately with our free tool.
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Accuracy & Review
Reviewed by: Maria Ramirez, PE
Maria is a licensed Professional Engineer (PE) with experience reviewing residential and light commercial concrete quantity takeoffs. She reviewed the formulas, unit conversions, rounding rules, and default yield assumptions used in this calculator.
Last updated:
See: Methodology · Data Sources · Review Board
Important Estimate Disclaimer
The results provided by this calculator are intended as general estimates only and should not be considered precise engineering measurements. Actual material requirements, costs, and quantities can vary significantly based on site conditions, local building codes, soil type, reinforcement requirements, climate exposure, and the intended use of your project.
These calculators are designed to help you plan and budget your project more effectively, but they do not replace professional advice from a qualified contractor, engineer, or building inspector. Always verify your calculations and assumptions with trained professionals before placing material orders or commencing construction.
For more information on the assumptions, formulas, and data used in these tools, see our Data Sources and Methodology pages.
Material estimates, cost figures, and volume calculations are approximate and may not reflect your actual requirements. Always double-check dimensions and project-specific needs, and consider adding a contingency allowance for waste, over-excavation, and unforeseen conditions.
If you are unsure about any aspect of your project — including structural requirements, reinforcement needs, drainage, or load-bearing capacity — consult with a licensed professional before proceeding.