Rebar Calculator: Cutting, Weight, Spacing & Cost
Estimate rebar cut lengths, quantities, total weight, spacing layouts, waste, and project cost in one place. Enter bar size, dimensions, spacing, laps, hooks, stock lengths, and rates to generate summaries plus CSV and PDF exports.
Developed by: Nohman Habib
Example Data
| Example | Mode | Bar Size | Inputs | What you get |
|---|---|---|---|---|
| Slab mat | Slab mat | 12 mm | Panel 6 m × 4 m, cover 0.04 m, spacing 0.15 m both ways, lap 0.60 m, hooks 0.20 m, waste 5% | Bars per direction, cut length per bar, total length, weight, stock bars, drop, and cost totals |
| Single set | Single bar set | 16 mm | Qty 20, bar length 4 m, lap 0.60 m, hooks 0.20 m, waste 5%, stock 12 m | Cut length per bar, total length with waste, weight, stock bars, estimated drop, and cost breakdown |
Formula
- Cut length per bar = Base length + Lap allowance + Hook/ends allowance
- Total length = Cut length per bar × Quantity (or sum of both slab directions)
- Total length with waste = Total length × (1 + Waste% / 100)
- Unit weight (metric) ≈ d² / 162 (kg/m), where d is diameter in mm
- Total weight = Total length with waste × Unit weight
- Stock bars (simple) = ceil(Total length with waste / Stock length)
- Estimated drop = (Stock bars × Stock length) − Total length with waste
- Total cost = Material + Fabrication + Placement
How to Use This Calculator
- Select your unit system and choose a calculation mode.
- Pick a bar size (or set a custom diameter in metric mode).
- For a single bar set, enter quantity and base bar length.
- For a slab mat, enter panel size, cover, and spacings for both directions.
- Add lap, hook allowances, and a waste percentage.
- Optionally enter stock bar length and your rates for cost breakdown.
- Click Calculate to see results above the form, then export CSV or PDF.
FAQs
1) What does “cut length” include in this calculator?
Cut length is the base bar length plus any lap splice allowance and hook or end allowance you enter. Use it as a practical cutting length for a rebar schedule or site cutting list.
2) How is rebar weight calculated?
The calculator multiplies total length (including the waste factor) by unit weight. In metric mode it uses the common approximation d²/162 in kg per meter. In imperial mode it uses standard lb/ft tables converted to kg/m.
3) How does the slab spacing takeoff work?
It reduces the panel dimensions by two times the clear cover, then counts bars as floor(effective dimension / spacing) + 1 in each direction. It totals lengths for both directions and adds lap and hook allowances per bar.
4) What is the waste percentage used for?
Waste increases the calculated total length and weight to account for offcuts, overlaps, damage, and practical site loss. If you also use stock length, the estimated drop helps you judge waste more realistically.
5) Is the “stock bars needed” value an optimizer?
No. It is a simple takeoff: total length with waste divided by stock length, rounded up. True cutting optimization depends on bar marks and mixed cut lengths. Use this for quick estimating.
6) Can I estimate total cost with labor and fabrication?
Yes. Enter material rate per kg, placement labor per kg, and fabrication per kg and/or cost per bend. The calculator provides line-item subtotals and a grand total based on the computed total rebar weight and quantity.