Size welded wire mesh for a slab without guessing at the store. Enter the slab dimensions, choose flat sheets or rolls, and get the piece count with the standard one-square lap overlap included.
Wire Mesh Calculator
Standard pieces: flat sheets 5 × 10 ft, rolls 5 × 50 ft and 5 × 150 ft. Mesh must lap one full square at every joint.
You need
Mesh weight varies by wire gauge (6×6 W1.4×W1.4 is the common slab mesh). Check the bundle weight at the yard, and never let mesh rest on the ground; chair it or pull it up during the pour.
A wire mesh calculator divides the slab area by the coverage of one sheet or roll, then adds an allowance for laps and cuts. A standard sheet covers 50 sq ft, so a 20 × 20 ft slab needs 8 sheets exact and 9 with the standard 10% lap allowance. Enter your slab above for sheets or rolls.
How to Calculate Wire Mesh for a Slab
Welded wire mesh is the fast alternative to tying a rebar grid: sheets or rolls of pre-welded wire that control shrinkage cracking across a whole slab. Ordering it looks like simple area math, and it nearly is, except every joint must lap at least one full square, edges get trimmed, and rolls unroll with a memory that eats coverage. This wire mesh calculator builds those realities into the piece count.
The Formula
Pieces = area × (1 + lap allowance) ÷ coverage per piece, rounded up
Sheet = 50 sq ft (5 × 10 ft) · Small roll = 250 sq ft · Large roll = 750 sq ft
The one-square lap rule: where two pieces meet, overlap them by one full mesh square (6 in on 6×6 mesh) plus a wire, and tie the lap. Laps in both directions are why flat area division always under-orders by roughly 10%.
Worked Example: 20 × 20 ft Slab in Flat Sheets
Area = 400 sq ft. Sheets exact = 400 ÷ 50 = 8. With the 10% lap-and-cut allowance: 440 ÷ 50 = 8.8, round up to 9 sheets. In rolls the same slab is 2 small rolls (250 sq ft each), one roll leaves you 150 sq ft short, which is exactly the mid-pour store run this calculator exists to prevent.
Mesh Styles You Will Meet at the Yard
| Style | Wire size | Common format | Typical use |
|---|---|---|---|
| 6×6 W1.4×W1.4 | 10 gauge | Sheets & rolls | Standard slab-on-grade mesh |
| 6×6 W2.0×W2.0 | 8 gauge | Sheets | Driveways, heavier slabs |
| 6×6 W2.9×W2.9 | 6 gauge | Sheets | Commercial slabs |
| 12×12 W1.4 | 10 gauge | Rolls | Light residential, overlays |
The W number is the wire cross-section in hundredths of a square inch. W1.4 means 0.014 sq in, roughly 10 gauge. If the drawing specifies a style, match it exactly; mesh is specified by wire area, not by the grid size alone.
Why the Lap Allowance Is Not Optional
Every sheet joint laps a full square, every roll end laps, and every edge against a form gets trimmed or folded. On a small slab those laps are a bigger share than on a warehouse floor, which is why the allowance is a percentage you set: 10% suits rectangular slabs in sheets, 15% suits rolls (end waste and curl trimming) and small cut-up areas with many edges.
How to Measure and Calculate: Step by Step
- Measure the slab length and width in feet, inside the forms.
- Choose the format your supplier stocks, sheets for small slabs, rolls for long runs.
- Set the lap allowance: 10% for sheets, 15% for rolls or cut-up shapes.
- Enter the figures above and round the piece count up, never down.
- Add chairs or plan to lift the mesh into the middle third of the slab as you pour.
Worked Example 2: 40 × 5 ft Sidewalk in Rolls
Area = 200 sq ft. A 5 ft wide roll matches the sidewalk width exactly, so coverage is honest: 200 ÷ 250 = 0.8, one small roll covers it with length to spare for the end laps. In sheets it would be 200 × 1.10 ÷ 50 = 4.4, so 5 sheets and twenty laps to tie. Long narrow work is where rolls win.
Common Quantities at a Glance: Cheat Sheet
| Job / quantity | Result |
|---|---|
| 10 × 10 ft slab, sheets | 3 sheets with laps |
| 20 × 20 ft slab, sheets | 9 sheets with laps |
| 20 × 20 ft slab, small rolls | 2 rolls |
| 30 × 40 ft slab, sheets | 27 sheets with laps |
| 30 × 40 ft slab, large rolls | 2 rolls |
| One sheet 5 × 10 ft | 50 sq ft coverage |
Practical Tips From the Job
Unroll rolls the day before and weigh the ends down, or they will curl back at you all pour long. Keep mesh 2 inches clear of forms at edges, tie laps at every second wire, and walk on boards once it is placed, a grid flattened by boots before the pour stays flat in the slab.
Common Mistakes to Avoid
- Dividing area by sheet size and ordering exactly that count.
- Overlapping mesh by ‘a few inches’ instead of a full square.
- Leaving mesh on the ground, it must sit in the slab, on chairs.
- Cutting sheets to exact size with no allowance for edge trim.
- Using light patio mesh where the drawing specifies a heavier W number.
What It Costs and How to Order Smart
Mesh is priced per sheet or per roll, so the piece count is the quote: 9 sheets for the 20 × 20 example. Compare formats on price per covered square foot including the lap allowance, not the sticker, a cheap large roll that leaves 300 sq ft unused is not cheap. Add chairs and tie wire; both are small, both are always forgotten.
Who Uses This Calculator?
Builders use this calculator to convert slab schedules into sheet and roll orders. Contractors compare sheet versus roll pricing with the lap allowance included. Engineers specifying WWR use the style table to sanity-check submittals. Architects detailing overlays use the light-mesh rows, and homeowners mesh a shed slab with the same count the yard will hand them.
Wire Mesh Calculator FAQs
How many sheets of wire mesh do I need for a 20×20 slab?
A sheet covers 50 sq ft and the slab is 400 sq ft, so 8 sheets cover it exactly, but laps and trims take about 10%, making the practical order 9 sheets. In rolls, the same slab takes 2 small 5 × 50 ft rolls. Order the extra sheet; a mid-pour shortage costs more than a return trip with a spare.
How much should wire mesh overlap?
At least one full square plus one wire, 6 inches plus on standard 6×6 mesh, tied at the lap. The lap is where two pieces act as one; a short lap is a crack line waiting at every joint. This calculator’s allowance assumes proper one-square laps in both directions.
Is wire mesh as good as rebar in a slab?
They do different jobs. Mesh controls shrinkage crack width across the whole slab and is ideal for light-duty 4 inch work. Rebar adds bending strength for loads, spans and poor ground. Many driveways use both: a rebar perimeter with mesh in the field. Follow the drawing when there is one.
What size wire mesh should I use for a driveway?
6×6 W1.4×W1.4 (10 gauge) is the baseline; step up to W2.0 wire or add a rebar grid where trucks park or the ground is fill. The heavier the vehicle and the worse the soil, the more steel the slab wants, mesh size comes from the design, not from what is on the shelf.
Does wire mesh need chairs?
Yes, if it is to work. Mesh must sit in the middle-to-lower third of the slab. Lying on the ground it does nothing, and ‘pulling it up with a hook’ during the pour leaves half of it on the bottom anyway. Chair it, or use mesh supports at edges and laps, before the truck arrives.
Sheets or rolls, which wire mesh is better?
Sheets lie flat, lap neatly and suit slabs under about 500 sq ft. Rolls cover long runs fast with fewer laps but fight you with curl and need weighting overnight. Price both formats per covered square foot with the lap allowance in, the calculator shows the piece counts to compare.
Can wire mesh replace fiber in concrete?
They overlap in purpose, both control plastic shrinkage cracking, but they are not interchangeable on a specified job. Fiber is mixed through the whole load; mesh is a placed layer. Some specs allow either, many require one or the other. Do not swap without the specifier’s agreement.
How do I cut wire mesh to size?
Bolt cutters for single wires, an angle grinder or reciprocating saw for production cutting. Cut from the full piece so offcuts stay usable, and keep cut edges 2 inches clear of the form face. Figure cutting waste into the allowance, irregular slabs with many cuts belong at 15%, not 10%.
How accurate is this wire mesh calculator?
Area and coverage are exact; the variable is lap and trim waste, which the allowance field handles. Rectangular slabs in the stated format land within one piece of the calculation in practice. For L-shaped or curved work, split the area into rectangles, calculate each, and add one spare piece.
Related Calculators
Sources used for standards and conversions: National Ready Mixed Concrete Association (NRMCA) guidance on ordering and yield; American Concrete Institute (ACI) practice for mix and placement; Portland Cement Association (PCA) design and control guidance; US manufacturers’ printed yields (80 lb bag = 0.60 ft³). Depths, sizes and spacings set by your local building code govern wherever they differ from the general figures here.
Disclaimer: Results are estimates for planning and ordering. Confirm quantities with your supplier before ordering, and have structural work, footings, walls, columns, beams and anything load-bearing, checked by a licensed engineer.