Concrete Slab Calculator
Enter the size and thickness of your slab, patio, driveway or pad to get the exact volume, the amount to order with waste, the number of bags if you mix by hand, and how many ready-mix trucks to schedule. Prices adjust to your state and every one can be edited.
Concrete Slab Calculator — ConcreteNear.com
| Slab area | 100 ft² |
| Concrete volume (exact) | 1.23 yd³ |
| Cubic feet | 33.3 ft³ |
| 80-lb bags (if mixing by hand) | 62 |
| 60-lb bags | 82 |
| Ready-mix trucks (10 yd³ each) | 1 |
| Approximate weight in place | 2.4 tons |
Cost estimate U.S. average prices
| Ready-mix concrete 1.5 yd³ × $160.00 | $240.00 |
| Short-load fee (last load 1.5 yd³ < 6 yd³) 1 load × $150.00 | $150.00 |
| Estimated total | $390.00 |
| Alternative: 80-lb bags instead of ready-mix 62 bag × $6.50 | $403.00 |
| Cross-check: Installed flatwork cross-check (4 in, public-works price) 100 ft² × $7.64 | $764.00 |
- That's 56 80-lb bags before waste (about 2.2 tons to lift and mix). A short-load or volumetric truck saves a lot of labor.
- Small pours often carry a short-load fee. Volumetric (mix-on-site) trucks let you pay only for what you pour.
| Inputs | |
| Shape | Rectangle / square |
| Length | 10 ft |
| Width | 10 ft |
| Thickness | 4 in |
| How many identical slabs | 1 |
| Extra for waste & over-excavation | 10% |
| Ready-mix truck size | 10 yd³ |
| Short-load minimum | 6 yd³ |
Planning estimate only — confirm with your supplier or contractor.
Prices used — edit any price to match your local quote
| Item | Unit price | Basis & source |
|---|---|---|
| Ready-mix concrete per yd³ | public source NRMCA Performance Benchmarking Survey — average 2023 U.S. selling price per cubic yard (2023 data) — Plant price before delivery, short-load, wait-time and fuel fees. Concrete Financial Insights reports $179.95/yd³ for 2025 across four public producers (likely higher than small residential pours). | |
| Short-load fee (per truck under the minimum) per load | starting estimate Starting estimate. Ready-mix producers charge a flat or per-yard fee for small loads; ask your dispatcher. | |
| 80-lb bag of concrete mix per bag | starting estimate Starting estimate for a retail shelf price. Check your store. | |
| Installed concrete flatwork, 4 in per ft² | derived from source Florida DOT Item Average Unit Cost 2025, item 0522 1 Concrete Sidewalk and Driveways, 4" — $68.76/yd² (156 contracts) (2025 lettings) — $68.76 ÷ 9 ft²/yd². Florida public-works price, scaled to your state; a cross-check, not a quote. |
How to use this calculator
- Measure the length and width of the forms (or the diameter for a round pad).
- Enter the slab thickness — 4 in for patios and walks, 5–6 in for driveways that carry trucks.
- Add 5–10% extra for uneven subgrade and spillage.
- Read the order quantity, bags and trucks, then compare ready-mix and bag cost.
Formulas
Volume (ft³) = length × width × thickness (in) ÷ 12Cubic yards = ft³ ÷ 27Order = yd³ × (1 + waste %), rounded up to the next ¼ yd³Round slab: area = π × (diameter ÷ 2)²
Questions
How many yards of concrete do I need for a 10×10 slab?
A 10 × 10 ft slab 4 in thick is 33.3 ft³, or 1.23 yd³. With 10% extra, order 1.5 yd³ (rounded up to the next ¼ yard).
How thick should a concrete slab be?
4 in is common for patios, walks and garage floors for cars; 5–6 in for driveways that see trucks or RVs. Follow your local code or engineer for structural slabs.
Is it cheaper to buy bags or order ready-mix?
Below about 1 yd³, bags usually win. Above that, ready-mix is usually cheaper and far less work — but watch for short-load fees on small orders. The calculator shows both.
Sources & assumptions
Prices checked 2026-11-10. State pricing multiplies national figures by the U.S. Bureau of Economic Analysis regional price parities (goods for materials, services for labor and services). RPPs compare general consumer price levels (U.S. = 100). They are not construction-specific; we use RPP Goods for materials and RPP Services: Other (excludes rents) for labor and services.
- Ready-mix concrete — NRMCA Performance Benchmarking Survey — average 2023 U.S. selling price per cubic yard (2023 data). Plant price before delivery, short-load, wait-time and fuel fees. Concrete Financial Insights reports $179.95/yd³ for 2025 across four public producers (likely higher than small residential pours).
- Installed concrete flatwork, 4 in — Florida DOT Item Average Unit Cost 2025, item 0522 1 Concrete Sidewalk and Driveways, 4" — $68.76/yd² (156 contracts) (2025 lettings). $68.76 ÷ 9 ft²/yd². Florida public-works price, scaled to your state; a cross-check, not a quote.
- Installed concrete flatwork, 6 in — Florida DOT Item Average Unit Cost 2025, item 0522 2 Concrete Sidewalk and Driveways, 6" — $104.10/yd² (194 contracts) (2025 lettings). $104.10 ÷ 9 ft²/yd².
Starting estimates No public price series was found for: Short-load fee (per truck under the minimum); 80-lb bag of concrete mix. These defaults are editable placeholders — replace them with a local quote.
Results are planning estimates, not quotes or engineering advice. Codes, specifications and your supplier's numbers govern.
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