First pair is grid spacing in inches; W number is wire area in hundredths of a square inch.
Slab 1
Advanced options
ACI 318 §25.5.4 for plain welded wire.
Mesh stops short of the slab edge.
Offcuts around penetrations and edges.
This wire mesh calculator works out how many sheets or rolls of welded wire reinforcement you need — with the lap splice included, which is why a 5 × 10 sheet doesn’t actually cover 50 square feet.
The short answer
A 5 × 10 ft sheet is 50 square feet nominal but covers about 40, because ACI requires an 8 inch lap on 6×6 mesh. That’s a 19% loss most calculators ignore.
A 20 × 20 ft slab needs about 11 sheets of 6×6 W2.0 — not the 8 you get from dividing 400 by 50.
On this page
How to use this wire mesh calculator
Pick your mesh designation, enter the slab, and the calculator returns sheets or rolls with the lap already accounted for. Four shapes:
- Rectangle — most slabs, driveways and pads
- L-shape — overall dimensions minus a cut-out
- Circle — round pads and tank bases
- Known area — you’ve already worked out the square footage
The toggle in the header switches between sheets and rolls. Under Advanced options you can change sheet or roll size, lap length, edge clearance and waste.
For a single rectangle, the results panel also shows the strict grid layout — how many sheets you’d physically lay if you never reused an offcut. That’s usually higher than the area-based figure, and the gap tells you how much cutting and reuse the job actually needs.
The lap splice everyone forgets
Welded wire sheets have to overlap. Butting them edge to edge leaves the reinforcement discontinuous exactly at the joint, which is precisely where a crack will form.
Lap = greater of (one mesh spacing + 2 in) or 6 in
6×6 mesh → 6 + 2 = 8 inches
4×4 mesh → 4 + 2 = 6 inches, so the 6 inch minimum governs
At least two cross wires from each sheet must fall within the splice.
The two-cross-wire requirement is the reason for the “plus 2 inches”. On a 6×6 mesh, an 8 inch lap guarantees a cross wire from each sheet sits inside the splice zone with enough beyond it to develop the wire. A 6 inch lap on 6×6 mesh can leave you with only one engaged intersection, which is not a splice.
What a sheet really covers
Lap on all four sides means the effective coverage is the nominal size minus one lap in each direction — not minus half, because adjacent sheets share each overlap.
| Sheet | Nominal | 6×6 mesh (8 in lap) | 4×4 mesh (6 in lap) |
|---|---|---|---|
| 5 × 10 ft | 50 ft² | 40.4 ft² −19% | 42.8 ft² −15% |
| 7.5 × 20 ft | 150 ft² | 132.1 ft² −12% | 136.5 ft² −9% |
| 8 × 20 ft | 160 ft² | 141.8 ft² −11% | 146.2 ft² −9% |
| Roll 5 × 150 ft | 750 ft² | 647 ft² −14% | 673 ft² −10% |
A 5 × 10 sheet loses 19% to lap; a 7.5 × 20 sheet loses 12%. The lap is a fixed width, so the smaller the sheet, the larger a fraction of it disappears into overlaps. On a big pour, larger sheets mean fewer splices, less waste and faster placement — the trade is that they need two people and won’t fit in a car.
How to read a mesh designation
6 × 6 — wire spacing in inches, longitudinal then transverse
W2.0 — wire cross-sectional area in hundredths of a square inch
So W2.0 = 0.020 in² of steel per wire. A “D” prefix means deformed wire.
You’ll still see the old gauge-based names in the trade and on some invoices. ASTM A1064 replaced the older A185 and A497 standards, and there’s no clean arithmetic relationship between gauge numbers and W numbers — you just have to know the pairs.
| Current designation | Formerly | Gauge | Wire area |
|---|---|---|---|
| 6×6 W1.4/W1.4 | 6×6-10/10 | 10 ga | 0.014 in² |
| 6×6 W2.0/W2.0 | 6×6-8/8 | 8 ga | 0.020 in² |
| 6×6 W2.9/W2.9 | 6×6-6/6 | 6 ga | 0.029 in² |
| 6×6 W4.0/W4.0 | 6×6-4/4 | 4 ga | 0.040 in² |
| 4×4 W1.4/W1.4 | 4×4-10/10 | 10 ga | 0.014 in² |
| 4×4 W2.9/W2.9 | 4×4-6/6 | 6 ga | 0.029 in² |
Which mesh for which job
| Application | Mesh | Why |
|---|---|---|
| Walkway, garden path | 6×6 W1.4 | Light crack control, no vehicle load |
| Patio | 6×6 W1.4 or W2.0 | W2.0 if the patio is large or the ground is unstable |
| Shed floor | 6×6 W2.0 | Point loads from equipment and shelving |
| Driveway | 6×6 W2.0 minimum | Vehicle loads — ACI 360R points to W2.0 or heavier |
| Garage slab | 6×6 W2.0 minimum | Same, plus concentrated jack and lift loads |
| RV pad, heavy vehicles | 6×6 W2.9 or rebar | Consider a rebar grid instead at this load |
| Stamped or decorative | 4×4 W2.0 | Tighter grid holds cracks tighter where appearance matters |
| Industrial floor | 6×6 W4.0 or rebar | Engineered design territory |
The calculator flags it if you pick 10 gauge mesh for something carrying vehicles. Stepping from W1.4 to W2.0 costs very little and increases the steel area by more than 40%.
Mesh weights
| Designation | lb per 100 ft² | 5 × 10 sheet | Roll 5 × 150 |
|---|---|---|---|
| 6×6 W1.4/W1.4 | 21 | 10.5 lb | 158 lb |
| 6×6 W2.0/W2.0 | 29 | 14.5 lb | 218 lb |
| 6×6 W2.9/W2.9 | 42 | 21.0 lb | 315 lb |
| 6×6 W4.0/W4.0 | 58 | 29.0 lb | 435 lb |
| 4×4 W1.4/W1.4 | 31 | 15.5 lb | 232 lb |
| 4×4 W2.0/W2.0 | 43 | 21.5 lb | 322 lb |
| 4×4 W2.9/W2.9 | 62 | 31.0 lb | 465 lb |
| 4×4 W4.0/W4.0 | 85 | 42.5 lb | 638 lb |
These are the figures suppliers quote, and they run 4–10% above what you get from wire area alone. That’s expected — published weights account for actual wire diameter tolerance and the edge wires, which the simple calculation misses.
Sheets or rolls?
Sheets
Lie flat
They stay where you put them and hold position while you pour. Standard for anything you care about. Heavier to handle and won’t fit in a car.
Rolls
Cheaper, but they curl
Easier to transport and less per square foot. The curl is a real problem — rolled mesh springs back and lifts off chairs unless you weight it down or cut and reverse-roll it first.
Rule of thumb
Sheets for slabs
Use rolls only on small, low-stakes pours where you can flatten them properly. On a driveway or garage floor, the placement advantage of sheets is worth the price difference.
Placement matters more than which mesh you buy
This is the single biggest failure with welded wire, and it’s extremely common. A slab in bending needs steel away from the neutral axis. Mesh lying on the vapour barrier at the bottom of the slab contributes almost nothing.
Pulling it up as the concrete goes in — “hooking” — does not reliably work either. It gets pulled to random heights, drops back where nobody is watching, and you have no way to check afterward. Buy the chairs. They cost a fraction of the mesh and determine whether any of it functions.
Practical placement:
- Position mesh in the upper third of the slab depth. For a 4 inch slab that’s roughly 1.25 to 1.5 inches from the top.
- Support on chairs or dobies at about 3 ft centres in both directions.
- Keep 2 inches clear of slab edges so the wire doesn’t rust at the perimeter.
- Lap and tie every splice — tie wire at intervals along the overlap, not just at the corners.
- Stagger the sheet joints rather than lining every splice up in one plane across the slab.
- Walk it before the pour and check nothing has been stepped down flat.
Mesh, rebar or fiber?
| Welded wire mesh | Rebar grid | Fiber | |
|---|---|---|---|
| Best for | Crack control in flatwork | Structural slabs, vehicle loads | Shrinkage cracking only |
| Steel area | Low to moderate | High | None |
| Placement | Fast — sheets drop in | Slow — cut and tie | Nothing to place |
| Stays put? | Only on chairs | Holds position well | Mixed in |
| Cost per ft² | $0.20–$0.45 | $0.55–$0.85 | $0.15–$0.25 |
Rebar has largely displaced mesh for driveways and garage slabs in residential work, mainly because it’s far easier to get right — a #4 grid on chairs holds its position, and an inspector can see at a glance that it has. Mesh remains the faster and cheaper choice for patios, walkways and light flatwork where crack control is the whole job.
Fiber controls plastic shrinkage cracking during curing and adds no structural capacity. It doesn’t replace steel on a load-bearing slab, though it’s a reasonable addition alongside it.
Sheets by slab size
6×6 mesh, 5 × 10 ft sheets, 8 inch ACI lap, 2 inch edge clearance, 10% waste.
| Slab | Area | Sheets | Weight (W2.0) |
|---|---|---|---|
| 8 × 10 ft | 80 ft² | 3 | 44 lb |
| 10 × 12 ft | 120 ft² | 4 | 58 lb |
| 12 × 20 ft | 240 ft² | 7 | 102 lb |
| 16 × 20 ft | 320 ft² | 9 | 130 lb |
| 20 × 20 ft | 400 ft² | 11 | 160 lb |
| 24 × 24 ft | 576 ft² | 16 | 232 lb |
| 12 × 60 ft driveway | 720 ft² | 19 | 276 lb |
| 30 × 40 ft | 1,200 ft² | 33 | 478 lb |
Areas shown are gross slab size; the calculator works from the clear area after edge clearance, which is slightly smaller.
Wire mesh mistakes to avoid
- Dividing area by the nominal sheet size. A 5 × 10 sheet covers about 40 ft², not 50.
- Butting sheets instead of lapping. No overlap means no continuity, at the exact point a crack wants to form.
- Leaving mesh on the ground. It contributes almost nothing at the bottom of a slab.
- Relying on hooking it up during the pour. Unreliable and impossible to verify afterwards.
- Using 10 gauge under vehicles. W2.0 is the practical minimum for driveways and garages.
- Rolls left curled. They spring back off the chairs while you’re not looking.
- Aligning every splice in one plane. Stagger them across the slab.
Frequently asked questions
How many sheets of wire mesh do I need?
Divide your slab area by the effective coverage of a sheet, not its nominal size. A 5 × 10 ft sheet covers about 40 ft² after an 8 inch lap, so a 400 ft² slab needs about 10 sheets before waste and 11 with a 10% allowance.
How much does a 5×10 sheet of wire mesh cover?
About 40 square feet with 6×6 mesh, or 43 with 4×4 mesh — not the 50 square feet of its nominal size. The lap splice on each side consumes roughly 19% of the sheet.
How much should wire mesh overlap?
ACI 318 §25.5.4 requires the greater of one mesh spacing plus 2 inches, or 6 inches. That’s 8 inches for 6×6 mesh and 6 inches for 4×4. At least two cross wires from each sheet must fall within the splice.
What does 6×6 W2.0 mean?
A 6 inch by 6 inch grid with wire of 0.020 square inches cross-sectional area in both directions — the W number is the area in hundredths of a square inch. It was formerly called 6×6-8/8, meaning 8 gauge wire.
What gauge wire mesh for a driveway?
6×6 W2.0 (8 gauge) as a minimum. ACI 360R guidance points to W2.0 or heavier for slabs carrying vehicles. The lighter W1.4 (10 gauge) is fine for patios and walkways but under-specified for a driveway.
Where should wire mesh sit in a slab?
In the upper third of the slab depth — roughly 1.25 to 1.5 inches from the top of a 4 inch slab — supported on chairs at about 3 ft centres. Mesh lying on the ground contributes almost nothing structurally.
Can I pull the mesh up as I pour?
It’s common practice and it doesn’t work reliably. Hooking pulls the mesh to random heights, it drops back where nobody sees, and there’s no way to verify placement afterwards. Chairs cost a fraction of the mesh and are the only dependable method.
How much does wire mesh weigh?
6×6 W2.0 weighs 29 lb per 100 square feet, so a 5 × 10 sheet is about 14.5 lb. Lighter 6×6 W1.4 is 21 lb per 100 ft², and heavier 6×6 W4.0 is 58.
Is wire mesh better than rebar?
For crack control in patios and walkways, mesh is faster and cheaper and does the job. For driveways, garage slabs and anything carrying vehicles, rebar is now standard — it has more steel area and holds its position far more reliably. Rebar has largely displaced mesh in residential slab work for that second reason more than the first.
Should I buy sheets or rolls?
Sheets, for anything that matters. Rolls are cheaper per square foot and easier to transport, but rolled mesh curls and springs off the chairs unless you flatten it properly. Sheets lie flat and stay put.
Do I need wire mesh in a 4 inch slab?
For a patio or walkway, mesh or fiber is usually adequate. For a garage slab or driveway, some reinforcement is standard practice and often required by local code — increasingly rebar rather than mesh. Reinforcement doesn’t prevent cracking; it holds cracks tight when they occur.
How do I cut welded wire mesh?
Bolt cutters for W1.4 and W2.0, or an angle grinder with a cutting disc for heavier wire. Cut on the ground, wear eye protection, and be aware that cut ends spring under tension. Leave enough beyond the last cross wire to make a proper lap at the joint.
Standards and sources
- ASTM A1064 — Steel wire and welded wire reinforcement, plain and deformed, for concrete (replaces A185 and A497)
- ACI 318 §25.5.4 — Lap splice requirements for welded plain wire reinforcement
- ACI 318 §25.5.5 — Lap splices for welded deformed wire reinforcement
- ACI 360R — Guide to design of slabs-on-ground, including minimum reinforcement for vehicle loads
- Published supplier weight tables, cross-checked against theoretical wire volume at 0.2836 lb/in³
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How this wire mesh calculator works out its numbers
Slab area is calculated from your dimensions less the edge clearance on each side. Effective sheet coverage is the nominal sheet dimensions less one lap width in each direction — one lap, not two, because adjacent sheets share each overlap. Lap defaults to the ACI 318 §25.5.4 minimum for plain welded wire: the greater of one mesh spacing plus 2 inches, or 6 inches. Sheets are then area divided by effective coverage, plus your waste allowance, rounded up.
For a single rectangular slab, the strict grid layout is also shown — the count you’d need laying whole sheets with no offcut reuse. Real jobs fall between the two figures depending on how much cutting you do.
Weights use published industry figures in pounds per 100 square feet. These run 4 to 10% above the theoretical value from wire area alone, because published figures account for actual wire diameter tolerance and edge wires.
This calculator produces quantities, not a reinforcement design. Mesh designation, wire size, spacing, slab thickness and cover for any structural slab must come from your local building code or an engineer’s drawings. Welded wire reinforcement controls shrinkage cracking; it is not a substitute for designed reinforcement in a load-bearing slab.