Slab Cost Calculator
Estimate slab cost — material, quantity and price with waste. Compare per yard, per bag or per ton for US projects. Enter dimensions, select units and add waste to get instant, supplier-ready numbers.
Enter dimensions above to calculate
- Enter values to see step-by-step substitution.
Engineering Assumptions:
- Quantity and quoted unit price must use the same unit. Tax applies to materials only in this model; local treatment of services and delivery may differ.
- Use a separate calculation for each material line and add the totals.
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TOP VIEW — Material quantity × Material price (optional)
SECTION — Delivery charge ($) 3in
What Is This Calculator?
The Slab Cost Calculator — Sizes slabs and patio concrete for US patios and shed pads — area, thickness, reinforcement and cost.
What Does It Calculate?
- Slab area in square feet
- Concrete volume in cubic yards
- Bags and reinforcement with waste
How to Use the Calculator
- Measure Slab Cost 20 ft x 10 ft x 4 in — use feet for length/width and inches for thickness where typical.
- Enter values and select units. The calculator converts to feet before calculating (inches /12, yards x3).
- Adjust waste % and optional price, then click Calculate. Results show with waste included.
- Use Reset to clear and try another size.
Formula & Engineering Methodology
Total = quantity × allowance factor × unit price × (1 + material tax / 100) + delivery + labor.
- L — Length for Slab Cost in feet
- W — Width for Slab Cost in feet
- D — Depth for Slab Cost in feet
All units convert to exact standard engineering dimensions (NIST SP 811) before calculation to ensure consistency between US Customary and Metric measurements.
Worked Example
Example: Slab Cost 20 ft x 10 ft x 4 in
| STEP | VALUE |
|---|---|
| Convert depth | 4 in /12 = 0.333 ft |
| Cubic feet | 20 x 10 x 0.333 = 66.67 ft3 |
| Cubic yards | 66.67 /27 = 2.47 yd3 |
| With 10% waste | 2.72 yd3 |
Construction Information
Material: Patio slabs 3.5–4 in thick, 3000–3500 psi. Base 4 in compacted gravel. Use welded wire mesh or rebar for crack control.
- Measure longest x widest; split L-shapes into two rectangles and add.
- Compact subgrade — soft spots add thickness.
- For structural sizing (beams, headers, rebar) verify with a professional per local code.
Material Information
Patio slabs 3.5–4 in thick, 3000–3500 psi. Base 4 in compacted gravel. Use welded wire mesh or rebar for crack control.
Waste & Overages
Add 5–10% for spillage and thickness variation — 10% safe for hand-screeded patios.
Practical Tips
- Slope patio 1/4 in per foot away from house
- Keep joints every 8–10 ft to control cracking
Common Mistakes
- Pouring too thin (under 3.5 in) — cracks and frost heave
- Forgetting slope — water pools against house
Assumptions & Engineering References
- Quantity and quoted unit price must use the same unit. Tax applies to materials only in this model; local treatment of services and delivery may differ.
- Use a separate calculation for each material line and add the totals.
This calculator provides an estimate based on your inputs. Actual requirements vary by site, material and installation. For code-regulated or load-bearing work, consult a qualified professional.
Calculations run 100% in your browser — zero tracking of your dimensions or input data.
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Frequently asked questions
What does the Slab Cost Calculator calculate?
The Slab Cost Calculator estimates slab cost quantity for US jobs — Slab area in square feet, Concrete volume in cubic yards, Bags and reinforcement with waste. Enter dimensions, choose units, add waste and price to get instant results.
How do I measure for slab cost?
Measure slab cost 20 ft x 10 ft x 4 in on site. Use the unit selectors — the tool converts inches→feet (÷12) and yards→feet (×3) before math. For non-rectangular, split into rectangles and add.
How much waste should I add?
Add 5–10% for spillage and thickness variation — 10% safe for hand-screeded patios.
How accurate is this slab cost estimate?
Math is exact for your inputs. Actual needs vary by site, material and installation. Add 5–10% waste for rectangular, 10–15% for irregular.
About Calculator Street
Built by Vipul Otari for US homeowners & contractors. Calculator inputs are processed in your browser. Estimates depend on your measurements, product specifications and the assumptions shown on this page. Confirm order quantities with your supplier and structural requirements with your project designer. Page updated: 2026-09-11.