Rebar Quantity Calculator

Work out rebar quantity instantly with clear inputs, formula shown and shareable results.

About Rebar Quantity Calculator

For a two-way mat the number of bars in each direction is the clear span perpendicular to them divided by the spacing, plus one because both edge bars are counted. Bar length is the slab dimension less cover at each end, and the totals give the running metres to convert into weight.

Formulas

Bar count

Bars = floor(clear width / spacing) + 1, taken in each direction

Running length

Total m = bars each way x their respective clear span

Worked example

With the default values below, Rebar Quantity Calculator returns Total bars required of 67. Change any input above and every figure here is recalculated in your browser.

Inputs used

Slab lengthminimum 0.1 m: 6 m
Slab widthminimum 0.1 m: 4 m
Bar spacing both waysminimum 25 mm: 150 mm
Side coverminimum 0 mm: 25 mm

Results

Total bars required: 67
Bars spanning the length: 27
Bars spanning the width: 40
Total bar length: 318.65 m

Step by step

1Values used
2Bar count
3Running length
4Total bars required= 67
5Bars spanning the length= 27
6Bars spanning the width= 40
7Total bar length= 318.65 m

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is the Rebar Quantity figure worked out?

Bars = floor(clear width / spacing) + 1, taken in each direction. For a two-way mat the number of bars in each direction is the clear span perpendicular to them divided by the spacing, plus one because both edge bars are counted.

Does this include laps and bends?

No. Add lap lengths where bars are spliced and hook or crank allowances from the bar bending schedule; those can add 5-10 percent to the running metres.

What values do I need to enter?

This calculator takes 4 inputs: Slab length, Slab width, Bar spacing both ways, Side cover. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.