Professional Rebar Stirrup Calculator 2026
Stirrups provide essential shear resistance in reinforced concrete columns and beams while maintaining proper spacing of main reinforcement bars. Accurate calculations determine cutting length per stirrup, total quantity based on member dimensions and spacing, and overall steel weight for material procurement. The calculator uses BS 8666 standards for hook lengths (9d minimum) and bend deductions ensuring compliance with UK fabrication tolerances.
Cutting length calculates as L = 2(A+B) + 2(hook length) - bend deductions where A = length and B = width after deducting clear cover. Hook length equals 9 × bar diameter or 75mm minimum per BS 8666 standards. Bend deductions include 3d for 135° hooks and 2d for 90° bends ensuring precise fabrication.
Number of stirrups = (member length ÷ spacing) + 1 accounting for the starting stirrup position. Typical column spacing ranges 100-150mm with closer spacing (75-100mm) in critical zones near supports. Beam stirrups use 100-150mm near supports and 200-300mm at mid-span where shear forces reduce.
Total weight = cutting length (m) × weight per metre × number of stirrups. Standard UK weights are 8mm = 0.395 kg/m, 10mm = 0.617 kg/m, 12mm = 0.888 kg/m. Add 5-10% wastage allowance for cutting losses and site variations.
135° hooks provide standard anchorage with length = 9d while 90° hooks use less material for lower shear demands. Hooks prevent stirrup opening under load and ensure concrete bond development. BS 8666 shape code 11 applies to rectangular stirrups with alternating hooks.
| Bar Size | Weight (kg/m) | Hook Length (9d) | 135° Deduction | 90° Deduction |
|---|---|---|---|---|
| 8mm | 0.395 | 72mm | 24mm (3d) | 16mm (2d) |
| 10mm | 0.617 | 90mm | 30mm (3d) | 20mm (2d) |
| 12mm | 0.888 | 108mm | 36mm (3d) | 24mm (2d) |
| Location | Spacing | Typical Size |
|---|---|---|
| Column Standard | 100-150mm | 8-10mm |
| Column Critical | 75-100mm | 8-10mm |
| Beam Support | 100-150mm | 8-10mm |
| Beam Mid-span | 200-300mm | 8-10mm |
L = 2(A+B) + 2(9d) - bend deductions. Internal dimensions deduct 2×clear cover.
(Length ÷ spacing) + 1. Always include starting stirrup.
8mm=0.395kg/m, 10mm=0.617kg/m, 12mm=0.888kg/m.
135° hooks, 9d length (min 75mm) per BS 8666.
Columns 100-150mm, beams 100-300mm varying by shear demand.
BS 8666: ±10mm cutting length, ±5° bend angles.
L = 2(A+B) + 2(9d) - (hook + corner deductions). Example: 300×250mm, 10mm bars, 25mm cover = 250×200mm internal, L=960mm.
(Height ÷ spacing) + 1. 3m column at 150mm spacing = 21 stirrups.
Cutting length (m) × kg/m. 960mm 10mm bar = 0.96×0.617 = 0.59kg.
Columns: 100-150mm standard, 75-100mm critical zones. Beams closer at supports.
135° standard hooks, length=9d or 75mm min. Alternate corners.
BS 8666 compliant fabrication: Heaton Manufacturing | Rebar calculator: RPO