Concrete Rebar & Mesh Grid Calculator
Calculate linear feet, 20-foot and 10-foot stock stick counts, grid intersections, support chairs, and wire ties for concrete slabs.
Concrete Rebar & Mesh Reinforcement Estimator
Universal calculator for US (#3, #4, #5) and UK/AU (N10, N12, N16) rebar.
280 ft grid + 120 ft perimeter (+10% splice)
Standard 20-foot sticks
Elevates steel to maintain concrete cover
Secures overlaps & bar intersections
Disclaimer: Calculations provided are estimates for preliminary material planning only. Actual yields vary based on subgrade compaction, site grading, waste, and local trade practices. QuickRenoTools assumes no liability for material shortages, structural failures, code non-compliance, vehicle overloads, or jobsite injuries. Verify all structural spans, retaining wall heights, and concrete mix designs with a licensed engineer, certified contractor, or local building authority prior to purchase and construction. Legal Disclaimer→
Rebar Grid Cheat Sheet (18-Inch / 450mm On-Center Spacing)
Quick reference showing rebar linear feet, 20ft sticks, 6m bars, and chair counts with 10% overlap splice buffer included.
| Slab Dimensions | Total Linear Steel | Stock Bars (20ft / 6m) | Rebar Chairs | Wire Ties |
|---|---|---|---|---|
| 10×10 ft (100 sq ft / 9.3 m²) | 154 lin ft (47 m) | 8 sticks (20ft) / 8 bars (6m) | 17 chairs | 54 wire ties |
| 12×12 ft (144 sq ft / 13.4 m²) | 238 lin ft (73 m) | 12 sticks (20ft) / 13 bars (6m) | 24 chairs | 90 wire ties |
| 12×16 ft (192 sq ft / 17.8 m²) | 304 lin ft (93 m) | 16 sticks (20ft) / 16 bars (6m) | 32 chairs | 109 wire ties |
| 20×20 ft (400 sq ft / 37.2 m²) | 616 lin ft (188 m) | 31 sticks (20ft) / 32 bars (6m) | 67 chairs | 216 wire ties |
| 24×24 ft (576 sq ft / 53.5 m²) | 898 lin ft (274 m) | 45 sticks (20ft) / 46 bars (6m) | 96 chairs | 318 wire ties |
Disclaimer: Calculations provided are estimates for preliminary material planning only. Actual yields vary based on subgrade compaction, site grading, waste, and local trade practices. QuickRenoTools assumes no liability for material shortages, structural failures, code non-compliance, vehicle overloads, or jobsite injuries. Verify all structural spans, retaining wall heights, and concrete mix designs with a licensed engineer, certified contractor, or local building authority prior to purchase and construction.
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Frequently Asked Questions: Concrete Rebar & Mesh Grid Calculator
Common questions about bag calculations, ordering bulk vs bags, and trade standards.
What size rebar is best for a residential concrete slab?
#4 rebar (1/2-inch diameter) is the industry standard for residential driveways, garage slabs, and heavy equipment pads. #3 rebar (3/8-inch) is acceptable for light sidewalks and 4-inch patio slabs.
What is the standard rebar grid spacing?
Standard residential grid spacing is 18 inches on center (O.C.) in both directions. For heavy vehicular loads or weak soils, structural engineers specify 12 inches O.C.
Why are rebar chairs mandatory during a pour?
Rebar provides tensile strength, but ONLY when suspended in the middle or bottom third of the slab. Placing rebar on dirt or trying to "pull it up" with a hook during the pour almost always fails. Plastic rebar chairs keep the steel elevated permanently.
How far from the slab edges should rebar be placed?
Keep rebar set back 2 to 3 inches from form boards and edges. If steel is too close to the outside edge, water can penetrate the concrete cover, causing the rebar to rust, expand, and spall the concrete.
How much should rebar overlap at splices?
Code requires rebar overlaps to equal 30 to 40 bar diameters. For #4 rebar (1/2" diameter), overlap sticks by at least 15 to 20 inches and secure them with two wire ties.
Is welded wire mesh better or worse than rebar?
Rebar is far superior structurally. Welded wire mesh (6x6-W1.4/W1.4) is flexible and frequently gets trampled to the bottom of the pour, offering zero crack resistance. Rebar stays rigid and resists heavy point loads.
What is the difference between Grade 40 and Grade 60 rebar?
Grade 60 rebar has a minimum yield strength of 60,000 PSI, which is 50% stronger than Grade 40 (40,000 PSI). Grade 60 is standard in modern residential and commercial construction.
How do you cut and bend rebar on the jobsite?
You can cut rebar using an angle grinder with a metal cutoff wheel, a reciprocating saw with a carbide blade, or a manual rebar cutter/bender. Slip a 3-foot length of steel pipe over the rebar to bend crisp 90-degree corner hooks.
Do I need rebar in a 4-inch concrete shed slab?
Yes. While unreinforced concrete can hold compressive weight, ground soil expands and contracts with moisture and winter frost. Rebar or heavy wire mesh holds the slab together if micro-cracks form.
How many rebar chairs do I need for my slab?
Place 1 rebar chair every 2.5 to 3 feet in each direction along the rebar grid, which equals approximately 1 chair for every 6 to 8 square feet of slab area.