How to use it
- Enter slab width in millimetres.
- Input the required concrete cover.
- Specify bar diameter and number of bars.
- Read the resulting uniform spacing in mm.
The Rebar Spacing Calculator quickly tells you the exact center‑to‑center distance between reinforcement bars for a given slab width, cover, bar size, and quantity. Knowing the spacing helps you verify that the concrete will meet structural requirements, avoid costly re‑work, and keep material waste low. You simply enter the slab width, the concrete cover you need, the diameter of the bar you’re using, and how many bars you plan to place. The tool assumes the bars are spread uniformly across the width, so the result is a single spacing value in millimetres. Use that number to set out the layout on site, to communicate with the supplier, and to double‑check compliance with your engineer’s design. The calculation is instant, accurate, and completely free.
Pro tips
- Add a small waste allowance (e.g., 5 mm) when ordering.
- Round up spacing to the nearest whole millimetre for easier layout.
- Verify that the spacing meets any project‑specific minimums before ordering.
- Double‑check that the bar count matches the design before finalizing.
Real-life examples
- A residential builder laying a 1200 mm wide concrete floor and needs bar spacing for a quick layout.
- An engineer reviewing a retrofit plan and wants to confirm uniform bar distribution across a slab.
- A contractor ordering reinforcement for a commercial patio and wants to avoid excess material.
Case study
John, a small‑job contractor, entered a 2000 mm slab width, 25 mm cover, 12 mm bars and 8 bars. The calculator returned 242 mm spacing, letting him mark the layout in minutes, order the exact quantity of steel, and finish the job two days ahead of schedule.