Mesh quantity can be estimated only after the reinforcement arrangement has been specified. The Whatson Rebar Mesh Quantity Calculator counts bars in two directions using the dimensions, cover, spacing, diameter and layers that you supply.
It does not determine whether that arrangement is strong enough for a slab or foundation. Read those requirements from the approved design.
What the edge cover does here
The calculator subtracts twice the entered cover from each overall dimension. It treats the remaining spans as a simple estimating geometry; it does not separately adjust bar centre lines for bar radius or crossing position.
Spacing X controls how many bars run along the length, distributed across the width. Spacing Y controls bars running along the width. The output schedule makes those directions explicit.
A clear span divided by spacing is rounded up to intervals. One bar is then added, placing a bar at each end of that model span. The actual interval spacing can therefore be smaller than the value you entered.
Read this one layer example
Use a 20 × 15 ft mesh, 25 mm cover, 150 mm spacing in both directions, 12 mm bars, one layer, zero lap and steel density 7,850 kg/m³.
The checked schedule has 32 bars along the length and 42 along the width: 74 bars altogether. Total cut length is 383.40 m. With a 5% weight allowance, the order estimate is 357.404 kg.
The input spacing describes a maximum interval in this counting method. It does not force an exact 150 mm grid with an unmeasured edge remainder.
The lap field is a simplified addition
Entered lap length is added once to every bar’s cut length. It is not a splice layout, and it does not calculate how many stock bars are needed along each run.
If some bars have multiple splices or different lap requirements, use a separate bar schedule with those lengths specified. A single shared lap cannot describe that variation accurately.
Before using the weight for procurement
Confirm the drawing’s directions, cover convention and number of layers. The tool uses one shared diameter for both directions; differing diameters need separate calculations or the Steel Bar Weight Calculator.
Chairs, links, edge reinforcement, openings, bends and local strengthening are outside this rectangular mesh count. The optional PKR per kg quote prices only the calculated weight with allowance.
Keep the direction table with the result. A total weight on its own cannot explain whether the bar count matches the intended layout.