Rebar Grid, Slab Mesh & Concrete Footing Reinforcement Calculator
Calculate concrete slab volume in cubic yards and cubic meters with customizable waste allowance, pre-mixed bag counts, rebar reinforcement, sub-base gravel, and itemized project costs.
Calculate exact concrete volume in cubic yards and cubic meters, pre-mixed bag quantities, rebar reinforcement grids, gravel sub-base, and itemized project costs.
10% recommended for residential slabs on compacted sub-base
Pre-Mixed Bagged Concrete Equivalents
Bag yield depends on manufacturer and aggregate mix. Always verify package specifications before ordering.
| Bag Size & Type | Approximate Yield | Net Bags | Order with Waste | Total Dry Weight |
|---|---|---|---|---|
| 80 lb (36.3 kg) bag | 0.60 cu ft (17 L) | 94 bags | 103 bags | 8,240 lbs (3,738 kg) |
| 60 lb (27.2 kg) bag | 0.45 cu ft (13 L) | 125 bags | 137 bags | 8,220 lbs (3,729 kg) |
| 50 lb (22.7 kg) bag | 0.375 cu ft (11 L) | 150 bags | 164 bags | 8,200 lbs (3,720 kg) |
| 40 lb (18.1 kg) bag | 0.30 cu ft (8 L) | 187 bags | 205 bags | 8,200 lbs (3,720 kg) |
| 50 kg (110 lb) bag | 0.85 cu ft (24 L) | 66 bags | 73 bags | 8,045 lbs (3,650 kg) |
| 25 kg (55 lb) bag | 0.42 cu ft (12 L) | 134 bags | 147 bags | 8,100 lbs (3,675 kg) |
Itemized Project Cost Estimator
| Concrete Material | $330.81 |
| Delivery / Short-Load Fee | $75.00 |
| Labor & Finishing | $350.00 |
| Equipment & Formwork | $100.00 |
| Sub-Base & Rebar Reinforcement | $0.00 |
| Estimated Total Project Cost | $855.81 |
Optional Reinforcement & Sub-Base Estimator
⚠️ Planning Estimates OnlyStructural calculations are for material planning and budgeting. Verify all reinforcement specifications with local building codes.
Steel Rebar Grid Reinforcement
Welded Wire Fabric (WWF Mesh)
Compacted Gravel Sub-Base & Leveling Sand
About Rebar Grid, Slab Mesh & Concrete Footing Reinforcement Calculator
Pouring a concrete slab represents a substantial investment in residential construction and landscaping. Whether building a backyard patio, foundation pad, walkway, or driveway, ordering exact concrete volume prevents costly shortages, delivery overages, and cold joints.
This Concrete Slab Calculator computes material quantities for single or multi-area slabs. It converts linear measurements into cubic yards, cubic feet, and cubic meters, models ready-mix truck loads alongside pre-mixed dry bag equivalents (40 lb, 60 lb, and 80 lb sizes), and estimates rebar grids, wire mesh, gravel sub-base, and itemized project costs.
For cylindrical footings, calculate volume with the concrete footing and post hole calculator and estimate base aggregate with the gravel calculator.
Step-by-step practical guide
- Choose your measurement system (Imperial feet and inches, or Metric meters and centimeters).
- Select a preset (Patio, Driveway, Garage Floor, Walkway, or Shed Pad) or enter custom dimensions.
- Select a slab thickness preset (4 in, 5 in, 6 in, 8 in, 10 in, or 12 in) or type a custom depth.
- Set a waste allowance percentage (10% is standard for compacted residential slab sub-bases).
- For multiple connected pads, click Add Another Area to combine project volumes into one order.
- Toggle Reinforcement and Sub-Base panels to calculate steel rebar grids, mesh, and base gravel.
- Review the itemized cost breakdown for ready-mix truck delivery or retail bag purchases.
Engineering specifications and execution details
Imperial slab volume: Volume (cu ft) = Length (ft) * Width (ft) * (Thickness (in) / 12).
Cubic yards conversion: Volume (cu yd) = Volume (cu ft) / 27.
Metric slab volume: Volume (cu m) = Length (m) * Width (m) * (Thickness (cm) / 100).
Conversion constants: 1 cubic yard equals 27 cubic feet (0.7646 cubic meters).
Bag yield constants: 80 lb bag yields 0.60 cu ft (45 bags per cu yd); 60 lb bag yields 0.45 cu ft (60 bags per cu yd); 40 lb bag yields 0.30 cu ft (90 bags per cu yd).
Rebar grid spacing: Bar counts = floor(Span / Spacing) + 1, including a 10% lap splice allowance.
Sub-base gravel density: Compacted gravel (#57 stone) is computed at 1.45 US tons per cubic yard.
Data privacy and memory isolation
All dimensional measurements, material pricing rates, and multi-area project totals run entirely client-side in your web browser memory.
No personal contractor estimates, job-site dimensions, or project cost figures are uploaded to remote servers or stored in third-party databases.
Common production use cases
- Homeowners deciding between bagged concrete mix and ready-mix truck delivery.
- Masons and flatwork contractors verifying yardage and delivery tickets before pours.
- Property owners budgeting material costs for driveways, patios, and shed foundations.
Edge cases and operational boundaries
- Pours over rough, uncompacted subgrade require an increased waste factor of 12% to 15% to prevent running short.
- Thickened perimeter footings or monolithic turn-down edges increase concrete volume beyond simple flat surface area formulas.
Frequently Asked Questions
How should control joints and expansion joints be spaced in concrete slabs?
Control joints should be spaced at a distance in feet roughly 24 to 30 times the slab thickness in inches. For a 4-inch slab, space joints every 8 to 10 feet in both directions. Cut joints to a depth of one-quarter the slab thickness within 12 to 24 hours of finishing to guide inevitable shrinkage cracking.
What rebar size and grid spacing are required for residential slabs?
Number 3 (3/8-inch) or Number 4 (1/2-inch) deformed steel rebar spaced 12 to 18 inches on center in a grid pattern is standard for residential driveways and patio slabs. Elevate rebar on plastic chairs to keep it suspended in the center or upper third of the concrete depth.
What is the difference between welded wire reinforcement (WWM) and steel rebar?
Welded wire mesh (such as 6x6-W1.4/W1.4) provides secondary crack control for light walkways and patios but cannot support heavy vehicle loads. Deformed steel rebar (#3 or #4) provides structural tensile reinforcement essential for vehicular driveways, garage slabs, and heavy equipment pads.
Why is a compacted gravel sub-base necessary under a slab?
A compacted crushed stone base of 4 to 6 inches (such as #57 washed stone or dense-graded aggregate) promotes drainage away from the slab underside, provides uniform soil load support, and mitigates frost heaving during sub-zero freeze-thaw cycles.
When is a polyethylene vapor barrier required beneath a concrete pour?
Interior slabs, garage floors receiving epoxy coatings, and heated basement slabs require a minimum 10 to 15 mil polyethylene vapor barrier directly over the sub-base. The barrier blocks upward soil moisture migration, protecting floor finishes from bubbling and efflorescence.
How does formwork bracing prevent blowouts during a large slab pour?
Hydrostatic pressure from wet concrete exerts substantial outward force on perimeter 2x4 or 2x6 form boards. Drive sturdy wooden stakes every 2 to 3 feet along exterior formwork and install diagonal kickers at all corners to maintain straight lines and prevent form blowouts.
What curing methods yield the highest compressive strength for exterior flatwork?
Continuous wet curing with water sprinklers or saturated burlap for the first 7 days produces maximum hydration and surface durability. Alternatively, applying a liquid membrane-forming curing compound directly after surface finishing locks in mixing moisture effectively.
What causes surface dusting and scaling on new concrete slabs?
Premature floating while bleed water remains on the surface weakens the surface water-cement ratio, creating a weak dusting crust. Excessive water in the mix, rapid surface drying in direct wind, or applying deicing salts during the first winter also trigger surface spalling.