Concrete Slab Calculator (2026) – Yards, Cost & Rebar
Calculate concrete for any slab, pad, patio, driveway, or garage floor. Get cubic yards, bag counts, 2026 cost by US region, and rebar quantity.
US avg $140–$225 in 2026
Slab Results
Adjust inputs and click Calculate
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Cubic Yards (with waste)
—Square Feet
—Est. Material Cost
—60 lb Bags Needed
—80 lb Bags Needed
Full Breakdown
Net volume—
Waste addition—
Rebar needed—
Region adj. cost—
→ Order this amount—
*Material cost only. Labor adds $2–$5/sqft. Always get 3 contractor quotes.
Common Concrete Slab Sizes — Quick Reference
| Project | Common Size | Thickness | Cubic Yards | Est. 80 lb Bags |
|---|---|---|---|---|
| Small patio | 10×10 ft | 4 in | 1.23 yd³ | 56 bags |
| Standard patio | 12×16 ft | 4 in | 2.37 yd³ | 107 bags |
| Large patio | 20×20 ft | 4 in | 4.94 yd³ | use ready-mix |
| 1-car garage | 12×20 ft | 4 in | 2.96 yd³ | use ready-mix |
| 2-car garage | 20×20 ft | 4 in | 4.94 yd³ | use ready-mix |
| Residential driveway | 10×20 ft | 6 in | 3.70 yd³ | use ready-mix |
| Sidewalk (50 ft) | 50×4 ft | 4 in | 2.47 yd³ | use ready-mix |
All figures include 10% waste factor.
Concrete Slab Cost by US Region (2026)
Total installed slab cost = concrete material + labor + finishing. Labor and finishing typically add $2–$5 per square foot on top of material cost.
| Region | Material ($/yd³) | Total Installed ($/sqft) | 10×10 Slab Total |
|---|---|---|---|
| Northeast | $175–$225 | $7–$12 | $700–$1,200 |
| West Coast | $165–$215 | $6–$11 | $600–$1,100 |
| Mountain West | $150–$190 | $5–$9 | $500–$900 |
| Midwest | $140–$175 | $4–$8 | $400–$800 |
| South | $130–$165 | $4–$7 | $400–$700 |
Slab Thickness by Application
- Sidewalks & walkways: 4 inches — ACI minimum for exterior flatwork
- Patios & pool decks: 4 inches — increase to 5 in if heavy furniture
- Garage floors: 4–6 inches — 6 in recommended for trucks/heavy vehicles
- Residential driveways: 4–6 inches — 6 in standard in cold climates
- Commercial driveways: 6–8 inches — for delivery vehicles and forklifts
Rebar & Wire Mesh Guide for Slabs
Rebar and wire mesh add tensile strength — concrete is strong in compression but weak in tension. For residential slabs, the choice is between rebar grids and fiber mesh additives:
| Method | Application | Spacing | Notes |
|---|---|---|---|
| #3 Rebar grid | Patios, sidewalks, garage floors | 12–18 in on center | Place at mid-depth (2 in up from bottom) |
| #4 Rebar grid | Driveways, commercial slabs | 12–24 in on center | Required where vehicle loads are expected |
| 6×6 Wire mesh | Patios, light-duty slabs | 6-in grid | Less effective than rebar but easier to install |
| Fiber mesh | All slabs | Mixed into concrete | Reduces plastic shrinkage cracks; doesn't replace structural rebar |
Concrete Slab FAQ
How many yards of concrete for a 20×20 slab?
A 20×20 slab at 4 inches thick = 400 sqft × 0.333 ft = 133.3 ft³ ÷ 27 = 4.94 yd³ net. With 10% waste = 5.43 yd³ to order. At $160/yd³ (Midwest average), material cost is ~$869. Use the calculator above for your exact thickness and region.
How thick should a concrete patio slab be?
4 inches is the ACI-recommended minimum for residential exterior flatwork including patios. Increase to 5–6 inches if the patio will support a hot tub (which can weigh 3,000–5,000 lbs when full), heavy planters, or a pergola with anchor bolts. Thicker slabs also reduce cracking risk in freeze-thaw climates.
How much does a concrete slab cost?
In 2026, a concrete slab costs $4–$8 per square foot installed in the Midwest/South, and $6–$12 per square foot in the Northeast and West Coast. A 10×10 patio slab typically costs $400–$1,200 total installed. Material alone (concrete + rebar) is usually $1–$3/sqft; labor and finishing account for the rest.
Do I need rebar in a 4-inch concrete slab?
For most residential patios and sidewalks, #3 rebar at 18-inch spacing or 6×6 wire mesh is recommended but not always code-required. For garage floors and driveways (where vehicle loads apply), rebar is strongly recommended. In freeze-thaw climates, rebar significantly reduces cracking from ground heave. Check your local building code — some municipalities require rebar for any slab over a certain size.