Rebar Calculator
Calculate the number, total length, and weight of reinforcement bars for a two-way slab or footing grid.
- Free to use
- Accurate results
- No registration required
- Works on all devices
Enter your slab dimensions, bar spacing, and bar diameter to find the total rebar length and weight needed.
Your result
149.33
Total weight
Total bar length168
Bars running lengthwise21
Bars running widthwise28
AI explanation
Formula
Bars in each direction = (opposite dimension ÷ spacing, rounded up) + 1; weight per meter = diameter² ÷ 162 (IS 1786)Worked example
4m × 3m slab, 150mm spacing, 12mm bars
| Field | Value |
|---|---|
| Slab/footing length (m) | 4 |
| Slab/footing width (m) | 3 |
| Bar spacing (mm, both directions) | 150 |
| Bar diameter (mm) | 12 |
| Bars running lengthwise | 21 |
| Bars running widthwise | 28 |
| Total bar length | 168 |
| Total weight | 149.33 |
Assumptions
- Assumes a simple two-way orthogonal grid with the same spacing in both directions — for different spacing per direction, run this calculator twice (once per direction) and add the results.
- Uses the standard IS 1786 weight-per-meter formula for TMT reinforcement bars.
Frequently asked questions
What bar spacing should I use?
Bar spacing and diameter come from your structural design based on the load and slab thickness — always follow your structural engineer's specification rather than a default.
Does this include laps or development length at bar ends?
No — this gives the raw grid length only. Add extra length for laps/development length at bar ends and edges per your structural drawing.
What is the IS 1786 weight formula?
Weight per meter (kg/m) = diameter² (mm) ÷ 162 — a standard formula for calculating the theoretical weight of TMT reinforcement bars from their nominal diameter.