Formula Used
Unit weight: d² ÷ 162.162 = kilograms per metre.
Total steel weight: total cutting length × unit weight.
Bars across a member: floor(usable dimension ÷ spacing) + 1.
Order quantity: net requirement × (1 + waste percentage ÷ 100).
The calculator converts every entered dimension into metres. It then builds each reinforcement group from spacing, cover, layers, faces, laps, hooks, and quantities. The final schedule combines automatic and manual rows accurately.
Stock-bar estimates divide each row’s cutting length by the chosen stock length. Offcuts are reported separately from the selected waste allowance. Actual optimisation can change after detailed cutting plans are prepared.
How to Use the Calculator
- Select the reinforcement mode and measurement system.
- Choose the main rebar diameter and steel grade.
- Enter member dimensions, spacing, cover, layers, or quantities.
- Set stock length, lap rules, hooks, and waste allowance.
- Add custom bar-bending rows when separate shapes are required.
- Enter pricing, tax, delivery, and labour information.
- Calculate, review the schedule, then export or print results.
Example Data
| Example | Key inputs | Typical use |
|---|---|---|
| Slab | 6 m × 4 m, 200 mm spacing, 40 mm cover, 12 mm bars | Two-way slab mesh |
| Wall | 8 m × 3 m, two faces, 200 mm spacing, 10% openings | Vertical and horizontal wall steel |
| Beam | 5 m long, 300 × 500 mm, four main bars, 150 mm stirrups | Main bars and closed links |
| Footings | 2 m × 2 m, two layers, four footings, 150 mm spacing | Repeated foundation reinforcement |
Standard Rebar Weight Reference
| Diameter | Approximate weight | 12 m bar weight |
|---|---|---|
| 6 mm | 0.222 kg/m | 2.66 kg |
| 8 mm | 0.395 kg/m | 4.74 kg |
| 10 mm | 0.617 kg/m | 7.40 kg |
| 12 mm | 0.888 kg/m | 10.66 kg |
| 16 mm | 1.579 kg/m | 18.94 kg |
| 20 mm | 2.467 kg/m | 29.60 kg |
| 25 mm | 3.854 kg/m | 46.25 kg |
| 32 mm | 6.315 kg/m | 75.78 kg |
| 40 mm | 9.867 kg/m | 118.40 kg |
Frequently Asked Questions
What does the calculator estimate?
It estimates bar counts, cutting lengths, weights, stock bars, waste, and costs. It also creates a practical bar bending schedule. Final reinforcement must follow approved structural drawings.
Which rebar weight formula is used?
The calculator uses d² divided by 162.162 kilograms per metre. Diameter is entered in millimetres. Published manufacturer values may differ slightly.
How are slab bars counted?
Concrete cover is removed from the member dimensions first. Usable width is divided by spacing. One final bar is then added.
How are laps calculated?
Automatic laps use a selected diameter multiplier. Manual laps accept a direct entered length. Required laps depend on design conditions.
Does waste include stock-bar offcuts?
The chosen waste percentage is applied to net calculated steel. Stock-bar offcuts are displayed as another estimate. Avoid counting the same loss twice.
Can different diameters be combined?
Yes, additional schedule rows support separate diameters and shapes. Each row receives its own unit weight. Totals combine every valid reinforcement row.
Can imperial dimensions be entered?
Yes, major dimensions use feet in imperial mode. Spacing, cover, hooks, and laps use inches. Diameters remain displayed in millimetres.
How accurate is stock optimisation?
The result is an estimating-level stock quantity. Detailed cutting combinations can reduce actual offcuts. Verify final orders against fabrication schedules.
Can this replace structural design?
No, this calculator supports quantity estimating only. It does not verify strength or code compliance. A qualified engineer must approve reinforcement designs.
Important Notice
This tool provides estimating results from the supplied inputs. Bar laps, hooks, covers, grades, and bending dimensions vary by code. Confirm every value before ordering or fabrication.
Supplier tolerances and cutting practices can change delivered quantities. Structural drawings and approved schedules always take priority. Professional review remains essential for construction work.