Reinforcing mesh calculator

How it works

Choose the documented local sheet type and enter the slab length, width, lap between adjacent sheets and maximum bar-chair spacing. The calculator compares both sheet orientations and chooses the grid with fewer whole sheets. It does not reuse trimmed offcuts, so treat the result as a conservative rectangular take-off.

The sheet dimensions are sourced separately for each country. The listed Australian SL72 and SL82 sheets are 6.0 x 2.4 m. The listed UK A142 and A193 sheets are 4.8 x 2.4 m. Suppliers may carry other sizes or product variants, so confirm that the selected sheet is available before ordering.

Enter a lap value from the structural drawings or reinforcement supplier. The calculator counts sheet-to-sheet joints in its chosen grid, it does not choose a lap length, decide which wires must overlap or check whether the reinforcement design is suitable.

Bar chairs are estimated as a rectangular grid with points along both slab edges and gaps no greater than your entered spacing. No general UK spacing value is assumed. Enter the spacing from the project design or your reinforcement supplier.

Formula

• Calculate the slab area

  Slab area = slab length × slab width

  Use the rectangular slab dimensions entered in the worksheet.

• Count sheets in each orientation

  1 + ceil((dimension − sheet size) ÷ (sheet size − lap))

  A dimension that fits one sheet uses one sheet. Repeat for both slab dimensions and both sheet orientations, then choose the layout with fewer whole sheets.

• Count sheet joints

  (sheets along length − 1) × sheets across + (sheets across − 1) × sheets along length

  This counts adjacent sheet-to-sheet joints in the selected grid.

• Estimate bar chairs

  (ceil(slab length ÷ chair spacing) + 1) × (ceil(slab width ÷ chair spacing) + 1)

  The estimate assumes support lines at the perimeter and equal spacing between them.

• Estimate tie wire when a rate is supplied

  Tie wire kg = slab area × entered rate in g/m² ÷ 1,000

  If no project or supplier rate is entered, tie wire is shown as not estimated.

Worked example

1. 1

   Set the example inputs

   4 m × 4 m slab, 200 mm lap

   Using A142 reinforcing fabric sheets sized 4.8 × 2.4 m, enter a 900 mm bar-chair spacing. The 200 mm lap is only an example input for showing the arithmetic, it is not a recommendation.

2. 2

   Count sheets, joints and chairs

   1 × 2 = 2 sheets, 1 lap joint, 36 bar chairs

   The slab area is 16 m². Tie wire is not estimated because no project or supplier rate was entered.

3. 3

   Check the spacing context

   The UK example enters 900 mm solely to demonstrate the count, this is not a recommended or code-approved spacing. Enter the spacing shown on the project design or specified by your reinforcement supplier.

Assumptions and limits

This tool is a material take-off, not a structural design. It does not select a reinforcement grade or layer, calculate bar size, check loads or soil conditions, set concrete cover, size edge beams, or decide sheet lap geometry. A structural engineer or approved project design must specify those details.

The cited UK product page verifies the sheet sizes and mesh grades, but does not establish a structural lap value or chair spacing.

An entered lap is applied in both sheet directions for the sheet-count estimate. The result counts adjacent sheet joints, not tie points. It does not calculate wire ties or determine the kilograms of tie wire from the number of joints. Enter a tie-wire rate only when a supplier or project specification provides one, otherwise the page reports that quantity as not estimated.

The bar-chair count is a grid estimate, not a fixing plan. It includes a row of supports along each slab edge and rounds each dimension up to enough equal intervals to stay within the entered spacing. Corners, penetrations, laps, mesh weight, construction access and the chair product can require a different layout or additional supports.

Sheet data names specific local products and stated dimensions, not every product stocked in that country. Verify the product, sheet dimensions, lap, chair type and pack size with the supplier and the project engineer before purchase or placement.

Frequently asked questions