10x20 Concrete Slab Concrete Calculator
A 10x20 slab covers 200 square feet with a 2:1 rectangular aspect ratio. Because concrete naturally shrinks during hydration, rectangular slabs of this length must be divided with a transverse control joint to prevent diagonal shrinkage cracking.
Custom 10x20 Concrete Slab Interactive Calculator
Pre-populated with 20 ft × 10 ft. Adjust thickness or unit system below for immediate real-time calculations.
Raw volume estimate. Standard practice is to add 5%–10% extra for form deflection, spillage, and uneven subgrade.
Rebar Grid & Control Joint Visualizer
Real-time scaled layout calibrated to ACI 318 structural concrete standards.
Ground Excavation & Gravel Subbase
Concrete flatwork requires excavating native soil to accommodate both the compacted gravel base and slab thickness.
Call-a-Batch-Plant Order Cheat Sheet
Concrete dispatchers move fast. Have these exact technical answers ready when placing your ready-mix delivery call.
Includes +10% waste buffer. Plants meter in 1/4-yard increments.
Air-entrained exterior flatwork mix (freeze-thaw & vehicle rated).
Standard workability for direct chute pours. If using a line pump, specify 3/8" pea gravel mix.
Suppliers typically include 5–7 mins/yard free unloading. Additional truck standby costs ~$2.50–$3.50/minute.
1. Project Dimensions & Area Specifications
| Length | Width | Thickness | Surface Area |
|---|---|---|---|
| 10.0 ft | 10.0 ft | 4.0 in | 100 sq ft (9.3 m²) |
2. Concrete Volume & Batch Order Requirements
| Net Calculated Volume | Recommended Order (+10% Waste) | 80-lb Pre-Mix Bags | 60-lb Pre-Mix Bags |
|---|---|---|---|
| 1.23 cu yds 33.3 cu ft / 0.94 m³ | 1.35 cu yds Ready-Mix Batch Plant Order | 56 bags | 74 bags |
3. Steel Reinforcement & Crack-Control Joint Schedule
| Rebar Specification | Grid Spacing | Bar Count | Linear Footage | Total Steel Weight | Control Saw Cuts |
|---|---|---|---|---|---|
| #4 Rebar (1/2" dia) | 18" On-Center | 14 total (7L + 7T) | 146 lin ft | ~98 lbs (+10% lap) | 0 cuts (max 10' spc, 1.0" deep) |
4. Jobsite Material Checklist
How It Is Calculated
For a slab measuring 10 ft long × 10 ft wide × 4 in thick:
- Normalize Dimensions to Canonical Base Unit (Meters)
Convert length, width, and thickness to meters using exact NIST international conversion factors.
Length: 20 ft = 6.096 m | Width: 10 ft = 3.048 m | Thickness: 4 in = 0.1016 m→ 6.096 m × 3.048 m × 0.1016 m - Calculate Volume in Cubic Meters
Multiply normalized length by width by thickness.
6.096 × 3.048 × 0.1016→ 1.8877897728000002 m³ - Convert Volume to Cubic Feet
Convert cubic meters to cubic feet using exact factor (1 cu ft = 0.028316846592 m³).
1.8877897728000002 / 0.028316846592→ 66.66666666666667 cu ft - Convert Volume to Cubic Yards
Convert cubic feet to cubic yards (27 cu ft = 1 cu yd).
66.66666666666667 / 27→ 2.469135802469136 cu yd
Concrete Volume & Bag Requirements by Depth
Concrete slabs are poured at different depths depending on intended vehicle or structural weight. The table below compares raw volume against recommended order volume (+10% safety buffer for uneven subgrade and form deflection).
| Thickness | Common Applications | Exact Yards | Order Yards (+10%) | 80 lb Bags | 60 lb Bags | Ready-Mix Logistics |
|---|---|---|---|---|---|---|
| 4″ | Standard Patio / Shed / Sidewalk | 2.47 yd³ | 2.72 yd³ | 123 | 163 | 2.72 yd³ (Short truck or small load) |
| 5″ | Residential Garage / Light Truck Pad | 3.09 yd³ | 3.4 yd³ | 153 | 204 | 3.40 yd³ (Short truck or small load) |
| 6″ | Heavy Equipment / Commercial / RV Pad | 3.7 yd³ | 4.07 yd³ | 184 | 245 | 1 truckload (41% of 10-yd mixer) |
Ideal Projects for a 10x20 Concrete Slab
- Single-car parking pad, car carport base, or driveway extension runner
- Long patio for outdoor entertaining, lounge seating, and cooking stations
- Boat, utility trailer, or lightweight camper parking pad
- Long tandem garden shed, greenhouse foundation, or shipping container pad
Gravel Subbase & Ground Prep Specifications
A durable concrete slab requires a solid, well-draining foundation to prevent settlement cracking and frost heave:
Compacted in 2-inch lifts with a mechanical plate compactor to 95% standard Proctor density. Use our dedicated Gravel & Subbase Material Calculator to estimate base depth for different soil types.
Reinforcement Schedule (#4 Rebar Grid)
Tensile reinforcement resists bending stresses from temperature fluctuations and heavy localized point loads:
Support rebar on approximately 34 concrete dobies or plastic rebar chairs to maintain reinforcement in the middle third of the slab. Alternatively, you may install 6x6 – W1.4/W1.4 welded wire reinforcement sheets (with 6" lap allowance). View our Concrete Rebar & Mesh Calculator for comprehensive cut lists.
Contraction Joint Layout (Crack Prevention)
Concrete inevitably shrinks as water evaporates during curing. Control joints create intentional weakened planes that dictate where microscopic hairline cracks occur, keeping them straight and unnoticeable:
Reference: ACI 302.1R Guide for Concrete Floor and Slab Construction recommends maximum joint spacing in feet equal to 2 to 2.5 times slab thickness in inches.
Estimated Cost for a 10x20 Concrete Slab
Covers ready-mix concrete delivery, gravel base, #4 rebar, lumber formwork, and stakes.
Includes excavation, subgrade prep, gravel compaction, rebar placement, pour, screeding, and professional broom/trowel finish.
DIY materials (ready-mix delivery, 4" compacted gravel base, #4 rebar, forms, expansion strips) cost between $850 and $1,400. Professional installation runs $8 to $13 per sq ft ($1,600 to $2,600) including site excavation, grading, base compaction, pouring, and broom finish. For detailed budget modeling including regional truck delivery fees and pump rentals, use our Concrete Cost & Budget Estimator.
Frequently Asked Questions: 10x20 Concrete Slab
How many yards of concrete for a 10x20 slab?
A 10x20 concrete slab at 4 inches thick requires 2.47 cubic yards of concrete (raw). Including a 10% safety margin for subgrade variation and form bulge, you should order 2.72 cubic yards. At 5 inches (recommended for vehicle parking), order 3.39 cubic yards.
Can you mix bags for a 10x20 slab?
Mixing bags for a 10x20 slab is strongly discouraged. A 4-inch 10x20 slab requires 123 bags of 80 lb concrete (or 163 bags of 60 lb concrete). At nearly 10,000 pounds of material, mixing bags would take many hours, resulting in cold joints where wet concrete cures against already-hardened concrete. A ready-mix transit mixer truck is the industry standard.
How thick should a 10x20 concrete parking pad be?
For passenger cars and small SUVs, a 4-inch slab on 4 inches of well-compacted gravel is acceptable. However, for full-size pickup trucks, utility trailers, or delivery vans, a 5-inch or 6-inch thickness with #4 rebar on 12-to-18-inch centers provides the load-bearing strength necessary to prevent wheel ruts and punch-through cracking.
Explore Other Popular Concrete Slab Dimensions
Need calculations for a different project size? Browse our complete engineering guides for popular slab footprints: