Wire Mesh Calculator

1. Enter the slab length and width in feet.
2. Enter the size of one piece of mesh: a sheet is often 10 by 5 feet, a roll often 150 by 5 feet.
3. Set a lap and waste allowance, about 10 percent for a rectangular slab, and the number of slabs.
4. Read the result: how many sheets or rolls to buy, and the area they cover.

Here is what each result line means:

A wire mesh calculator works out how much welded wire reinforcement a concrete slab needs, in whole sheets or rolls. Welded wire mesh, also called welded wire fabric or reinforcing mesh, is a grid of steel wires laid in a slab to control cracking and hold the concrete together once it does crack.

Because the mesh must overlap at the joins and is trimmed to fit, you always buy more than the bare slab area. The tool adds that allowance and divides by the coverage of one piece. To size the concrete the mesh sits in, use the concrete slab calculator, and to budget the pour the concrete slab cost calculator.

The slab area is length times width. Because sheets overlap and get cut, the mesh has to cover more than that bare area, so the tool multiplies by one plus the allowance, then divides by the area one piece covers.

1. Find the slab area, length times width, times the number of slabs.
2. Add the lap and waste allowance, usually about 10 percent.
3. Work out the coverage of one piece, its length times its width.
4. Divide the area with the allowance by the coverage per piece and round up to whole sheets or rolls.

A standard 10 by 5 foot sheet covers 50 square feet, so a 720 square foot slab with a 10 percent allowance needs 792 / 50, rounded up to 16 sheets.

Suppose you are reinforcing a slab 24 feet by 30 feet with 10 by 5 foot sheets and a 10 percent lap and waste allowance.

Calculation: the slab is 24 x 30 = 720 square feet. Adding 10 percent gives 792 square feet. Each 10 by 5 foot sheet covers 50 square feet, so 792 / 50 = 15.8, rounded up to 16 sheets, which buy 800 square feet of mesh.

The lesson: you buy about 16 sheets, not the 14.4 the bare area alone suggests, because the laps and cuts use real material.

Lap Length

Sheets overlap so the reinforcement is continuous. A common lap is one to one and a half mesh squares, so a larger lap, or a tighter grid, uses more mesh and raises the allowance.

Slab Shape

A plain rectangle wastes little; an L-shape, curves or many openings mean more cuts and offcuts. Use 15 percent for an irregular slab instead of 10.

Sheet Versus Roll

Sheets are easy to place flat and stay put; rolls cover long runs with fewer end laps but want flattening. The coverage per piece changes the count.

Edge Clearance

The mesh is kept back from the slab edge so steel does not reach the surface and rust, which slightly reduces the area it has to cover but is handled by the allowance.

Welded wire reinforcement comes as flat sheets or as rolls. They reinforce the same way; the choice is about handling and the size of the pour.

Enter whichever piece size you are buying, and the tool counts the pieces and the area they cover.

Ordering Mesh for a Slab

Work out the sheets or rolls to buy before you order, so you have enough for the laps without a wasted part-pallet.

Comparing Sheets and Rolls

Try both piece sizes to see which covers your slab with less waste and easier handling.

Budgeting the Reinforcement

Use the piece count with a price per sheet or roll to get the mesh cost before adding it to the slab budget.

1. Ordering the Bare Slab Area

The laps and cuts are real material. Buying only the slab area leaves you short, so always add the allowance.

2. Forgetting the Lap

Butting sheets edge to edge, with no overlap, breaks the continuity of the reinforcement. Lap by about one to one and a half squares and tie it.

3. Laying Mesh on the Ground

Mesh at the bottom of the slab does little. Support it on chairs or dobies so it sits in the slab, usually around the middle or upper third.

4. Running Mesh to the Edge

Steel that reaches the edge or surface rusts and stains. Keep the mesh back from the edges and the top.

5. Using One Allowance for Every Slab

A tidy rectangle needs about 10 percent; a cut-up, irregular slab needs more. Match the allowance to the shape.

The arithmetic is exact; the result depends on the piece size and the lap and waste allowance you enter, which vary with the slab shape and the specified lap.

Take the slab area, add about 10 percent for laps and cuts, then divide by the coverage of one piece. A 24 by 30 foot slab is 720 square feet, so with 10 by 5 foot sheets and a 10 percent allowance you need about 16 sheets. Enter your sizes above for the exact count.

A common sheet is 10 feet by 5 feet, which covers 50 square feet. Rolls are often 150 feet by 5 feet, about 750 square feet. Sheet and roll sizes vary by supplier and gauge, so check the product you are buying.

A common lap is one to one and a half mesh squares, with 6 inches as a practical minimum. Tie the overlap at the corners and once in the middle. Your plans or engineer may set a specific lap, so follow them where given.

A typical 150 by 5 foot roll covers about 750 square feet before laps. After a 10 percent allowance it effectively covers around 680 square feet of slab. The tool works this out from the piece size you enter.

Yes, roughly in the middle or the upper third, not on the ground. Support it on chairs or small concrete dobies so the concrete surrounds it. Mesh lying at the bottom of the slab does little to control cracking.

Light welded wire mesh controls shrinkage cracking in slabs on ground, while rebar carries structural loads. Many slabs use one or the other, and some use both. The right choice comes from your plans or an engineer, not from a quantity estimate.

It is a grid of steel wires welded at each crossing, sold by the wire gauge and the grid spacing, such as a 6 by 6 inch grid. A heavier gauge and a tighter grid give more reinforcement. Your plans specify the gauge and spacing to use.

No. The calculation runs entirely in your browser and nothing you enter is stored or sent anywhere.

• Hunker, how to reinforce concrete slabs with wire mesh (lap one to one and a half squares, support on dobies, keep off the edge).
• Concrete Reinforcing Steel Institute (CRSI) (CRSI; welded wire reinforcement for concrete).
• National Ready Mixed Concrete Association (NRMCA; concrete slabs and reinforcement context).