Wire Mesh Calculator
Find how many sheets or rolls of welded wire mesh to buy for a concrete slab. Enter the slab, the mesh size, and the lap to see the mesh to buy and how to lay it out. It works the same for welded wire fabric, remesh, and reinforcing mesh (reo mesh).
Add another rectangle for an L-shaped slab, or use Quantity for identical pads.
- Choose US or Metric. You can still change the unit of any single field.
- Enter the Length and Width of the slab. For an L-shaped slab, use Add section for each rectangle. For several pads of the same size, enter one and set Quantity.
- For a round slab or one with a curved edge, enter the rectangle around it, so the estimate comes out a little high.
- Choose the Mesh size you buy. For a sheet or roll that isn't listed, choose Custom sheet or Custom roll and enter its width and length from the label.
- Check the Lap and the Edge distance. They start at the defaults below, so enter the values on your plans if they give them.
- Optionally, enter the price of one sheet or one roll to estimate the cost.
Length fields accept whole numbers, decimals, fractions, and mixed
numbers, such as 20, 10.5, 1/2, or
1 1/2. Choose ft + in as the unit to enter
a slab length such as 20 ft 6 in in two fields.
How to calculate wire mesh for a slab
The calculator covers the inside of each section, the edge distance in from every edge, with rows of mesh. Each row is a strip as wide as the mesh, laid from one edge to the other. Pieces in a row overlap at their ends, and neighboring rows overlap at their sides, both by the lap:
Inside length = length − 2 × edge distance, and the same for the width
Rows = (inside side across the rows − lap) ÷ (mesh width − lap), rounded up
Pieces per row = (inside side along the rows − lap) ÷ (mesh length − lap), rounded up
Last piece = inside side along the rows − (pieces per row − 1) × (mesh length − lap)
If the side is no longer than the mesh, it takes one row, or one piece per row. Every piece in a row is a full sheet except the last one, which is cut to fit. The last row can be narrower than the mesh: trim it, and the trimmed strip isn't used.
Which way the mesh runs
For each section, the calculator tries the long side of the mesh along the section's Length and along its Width, and picks the way that takes fewer sheets or rolls. If both take the same number, it picks the way with less mesh laid, counting the laps. On a 20 × 10 ft slab, 5 × 10 ft sheets take 7 sheets along the length but 5 along the width. Square mesh such as 6x6, A142, or SL72 works the same both ways. The table under the result shows the way it picked for each section.
Sheets or rolls to buy
Sheets to buy = the full sheets in the rows + the sheets the last pieces are cut from
Last pieces of the same length are cut from one sheet, or one roll, as many times as they fit, across all the sections. On a roll, that's how many rows one roll gives you: a 5 × 150 ft roll gives 15 rows of 9 ft 9 in. Pieces of different lengths aren't combined, so you may need fewer if you plan the cuts. The count doesn't add extra mesh for cutting mistakes, so add one sheet if you want a margin.
Some calculators divide the slab area by the area of one sheet less the laps. That counts laps at the outside edges, where there are none, and can't tell when the last row fits. A 9 ft 7 in square slab takes two 5 × 10 ft sheets laid side by side, but 91.84 ÷ 40.44 = 2.27 rounds up to 3.
Sections that meet
Each section is counted on its own, with the edge distance at every edge, including where two sections meet. No lap is counted across that line. Splitting a slab into sections can come out lower than lapping the mesh across the line, or higher when each section has its own trimmed row.
To lap the mesh where two sections meet, enter one of them longer, across the line, by the lap plus twice the edge distance: 8 in + 3 in = 11 in with the US defaults, or 225 mm + 80 mm = 305 mm with the Metric ones. The inside of the two sections then overlaps by exactly the lap. The slab area comes out larger by that strip. For example, a 20 × 4 ft slab takes 3 sheets. As two 10 × 4 ft sections it takes 2, because nothing is lapped where they meet. Lapped there, two 120 in sheets can't cover the 237 in inside plus an 8 in lap. As 10 ft 11 in × 4 ft plus 10 × 4 ft, it takes 3 again. If the mesh stops where the sections meet, such as at a construction joint, enter the sections as they are.
Mesh sizes, laps, and edge distance
US mesh sizes
| Size | Description |
|---|---|
| 5 × 10 ft sheet | Flat sheets, 50 ft² each |
| 8 × 20 ft sheet | Large flat sheets, 160 ft² each |
| 5 × 150 ft roll | Rolled mesh you cut to length, 750 ft² each |
The US sizes are in every one of the three 6x6 styles (10, 8, and 6 gauge) listed in the US Commerce Department's 2020 investigation of standard welded wire mesh (Federal Register, Vol. 85, No. 144). The same list also has rolls of 5 × 50, 6 × 150, 5 × 200, and 7 × 200 ft, and sheets of 7 × 20 and 8 × 15 ft. Choose Custom sheet or Custom roll for those.
Metric mesh sizes
| Size | Description |
|---|---|
| 2400 × 6000 mm sheet | Standard sheet in Australia, 14.4 m² each |
| 2400 × 4800 mm sheet | Standard sheet in the UK, 11.52 m² each |
| 2000 × 3600 mm sheet | Smaller UK merchant sheet, 7.2 m² each |
The Metric sizes are written width × length in mm. Product names in the
UK and Australia often put the length first in meters, such as
4.8 x 2.4m or 6m (length) x 2.4m (width). The
2400 × 6000 mm sheet is the Australian size for SL72 and similar mesh,
from Reozone and iDlvr, and the default if your browser is set to
Australia or New Zealand. New Zealand sheets such as Steel & Tube's SE62
are a little larger, 6,040 × 2,440 mm, so counting with the 6000 mm sheet
doesn't leave you short. The 2400 × 4800 mm sheet is the UK A142 size,
and the 2000 × 3600 mm sheet is a smaller merchant size, both from
Jewson. The smaller sheet can leave less waste on a small slab, such as a
shed base.
How mesh is measured
The calculator uses the nominal size. In the US standard, the length is measured from the ends of the wires and the width between the centers of the outside wires. The wire ends that stick out past the outside wires vary by product, so they aren't counted.
Lap
The 8 in US default is one square of 6x6 mesh plus 2 in. The American Society of Concrete Contractors (ASCC) notes that ACI 318-19 calls for one square plus 2 in, or 8 in, for plain wire mesh in structural slabs, as does ACI 439.5R-18. It also reports a one-square lap, 6 in, that a designer accepted for a nonstructural slab on ground. For 4x4 mesh, one square plus 2 in is 6 in. The 225 mm Metric default is the lap for square mesh under the Australian residential slab standard AS 2870, as given by RMIT University and Reozone. A longer lap takes more mesh, so the defaults sit at the longer end.
The lap is used both between rows and between the pieces in a row. It's an estimate, not a code value: if your plans give a lap, enter it. The calculator doesn't check the lap against a code. A lap of 0 counts mesh butted edge to edge. The lap can be at most half the width of the mesh.
Edge distance
The edge distance is from the edges of the concrete to the edges of the mesh. The 1 1/2 in US default is the cover the US residential code (IRC R403.1.3.5.3) requires for No. 5 bars and smaller in concrete cast in forms that will be exposed to the earth or weather. Mesh wires are thinner than a No. 5 bar. The 40 mm Metric default is the cover for external exposure from RMIT University. Enter the cover on your plans. The calculator doesn't check it against a code.
Examples
A 20 × 10 ft slab with 5 × 10 ft sheets
With an 8 in lap and 1 1/2 in from the edges, the inside is 237 × 117 in. Along the width, the 117 in side fits in one 120 in sheet, and the 237 in side takes (237 − 8) ÷ (60 − 8) = 4.40, rounded up to 5 rows. You need 5 sheets, each cut to 9 ft 9 in. Along the length would take 7. At $12.98 a sheet, that's $64.90.
The same slab with a 5 × 150 ft roll
Each row is 117 in long, and a 1,800 in roll gives 1,800 ÷ 117 = 15.4, or 15 rows. The 5 rows take 1 roll.
A 12 × 12 ft slab
The inside is 141 in each way. That takes 3 rows of 2 sheets: a full 120 in sheet and a last piece of 141 − 112 = 29 in. Four 29 in pieces come from one sheet, so you need 4 sheets.
A Metric slab
A 6 × 4 m slab with a 225 mm lap and 40 mm from the edges is 5,920 × 3,920 mm inside. With 2400 × 4800 mm sheets along the width, it takes (5,920 − 225) ÷ (2,400 − 225) = 2.62, rounded up to 3 rows of one sheet: 3 sheets. With 2400 × 6000 mm sheets along the length, it takes 2.
FAQ
About 5 sheets of 5 × 10 ft mesh, with the long side across the slab, an 8 in lap, and 1 1/2 in from the edges. Laid the other way, it takes 7. One 5 × 150 ft roll also covers it.
Often one square plus 2 in, which is 8 in for 6x6 mesh, at the sides and ends. In Australia, square mesh is often lapped 225 mm. Use the lap on your plans if they give one.
In the US, 5 × 10 ft and 8 × 20 ft sheets and 5 × 150 ft rolls are common. In the UK, 2.4 × 4.8 m sheets, and in Australia, 2.4 × 6 m sheets. Enter any other size as a custom sheet or roll.
It depends on the wire size, so check the product label. Heavier wire doesn't change the number of sheets, so the calculator doesn't give the weight.
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