Rebar & Wire-Mesh Calculator
A 10×10 slab on a 16-inch grid (3-inch edge cover) needs 16 bars, about 152 linear feet, which is 8 sticks of 20 ft rebar, with 64 tie points. Pick your grid below, or switch to welded-wire mesh. This counts the steel for a grid you choose; it does not decide the bar size or spacing your slab needs.
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How the count works
The grid sits inside the slab edges by your edge cover (3 inches by default), so a 10×10 slab is reinforced over a covered 9.5 × 9.5 ft area. In each direction:
- Bars per direction = floor(covered span in inches ÷ spacing) + 1. The "+1" is the bar that closes the far side of the grid.
- Total linear feet = bars one way × their length, plus bars the other way × their length.
- 20 ft sticks = how many stock lengths you buy after cutting bars to size. A 9.5 ft bar yields two per stick; a bar over 20 ft needs a lap splice (about 12 inches).
- Tie-wire intersections = bars one way × bars the other way, the crossings you wire together.
Rebar for common slabs (16" grid, 3" cover)
| Slab | Total bars | Linear feet | 20 ft sticks | Tie points |
|---|---|---|---|---|
| 4×4 AC pad | 6 | 21 ft | 2 | 9 |
| 8×8 shed base | 12 | 90 ft | 6 | 36 |
| 10×10 patio | 16 | 152 ft | 8 | 64 |
| 10×12 patio | 17 | 178 ft | 13 | 72 |
| 12×12 patio | 18 | 207 ft | 18 | 81 |
| 10×20 parking pad | 23 | 299 ft | 16 | 120 |
| 24×24 garage | 36 | 846 ft | 72 | 324 |
Sizes past a single-car pad are where the stick count and the tie labor add up fast; a 24×24 garage grid is a bundle of steel, not a Saturday errand. Size the slab itself with the concrete slab calculator and the base with the gravel under concrete calculator.
Placing steel so it does its job
- Get it off the ground: rebar and mesh only work near the middle of the slab. Set them on chairs or dobies; steel lying on the base does nothing but rust.
- Lap the splices: overlap rebar about 12 inches (roughly 40 bar diameters) and mesh one full square, then tie the laps.
- Keep cover: hold steel 2 to 3 inches back from edges and up from the base so concrete surrounds it. Exposed bar rusts and spalls the slab.
- Mesh flat, not rolled: sheet mesh lies flatter than roll; if you use roll, reverse-bend it or weight it so it does not spring up into the finish.
FAQ
How much rebar do I need for a 10×10 slab?
On a 16-inch grid with 3 inches of edge cover, a 10×10 slab takes 16 bars, about 152 linear feet, which is 8 sticks of 20 ft rebar. That is 8 bars each way over the covered 9.5 × 9.5 ft area, crossing at 64 tie points. Tighten the grid to 12 inches and it climbs to 20 bars; open it to 24 inches and it drops to 10.
What size rebar and spacing does my slab actually need?
That is a structural call this tool does not make. Bar size (#3, #4, #5) and grid spacing come from your local building code or an engineer, and they depend on load, soil, and slab thickness. This calculator counts materials for a grid you enter. A common DIY patio grid is #3 or #4 bar at 16 to 18 inches, but confirm it before you pour anything that holds weight.
How many 20 ft sticks of rebar is that?
The tool cuts your bars from 20 ft sticks and counts how many sticks you buy, because raw footage alone does not tell you how many 20 ft stock lengths to order. A 9.5 ft bar yields two per stick, so 8 bars is 4 sticks; an 11.5 ft bar yields one per stick with a long offcut. Bars longer than 20 ft need a lap splice of about 12 inches (roughly 40 bar diameters), so buy extra length for those runs.
Rebar or welded wire mesh for a slab?
Both control cracking. Mesh is faster for flat patios and shed floors; a rebar grid carries more load for driveways and anything vehicles park on. Flip the tool to mesh mode and a 10×10 slab needs about 5 sheets (3.5 × 7 ft) or 22 ft off a 5 ft roll, including overlap. Whichever you use, keep it on chairs so it ends up mid-slab instead of lying on the base.
How much overlap for welded wire mesh?
Lap welded wire mesh at least one full square, about 6 inches, and tie the laps with wire. This calculator adds 10% to the slab area for those laps and trim waste. Hold the mesh roughly 2 inches back from the slab edges so steel is not exposed at the perimeter.