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Stirrup / Tie Calculator
Work out how many stirrups or ties a beam or column needs, plus the total rebar length, weight, and material cost, from your spacing and cover.
Covers cut waste, bent bar rejects, and field adjustments.
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Stirrup / Tie Calculator
Short answer: divide the beam’s usable length (total length minus the end offset at both ends) by the center to center spacing, then add one stirrup. A 12 ft beam with a 2 in offset and 8 in spacing needs about 19 stirrups, roughly 21.5 ft of bar once hooks and 5% waste are added.
Reference: typical stirrup spacing ranges
| Zone | Typical spacing | Notes |
|---|---|---|
| Near supports (high shear) | d/4 or per design | Tightest spacing, closest to columns or beam ends |
| Mid-span | d/2 or per design | Wider spacing where shear demand drops |
| Minimum practical spacing | 3 in to 4 in | Below this, congestion makes placing concrete difficult |
d is the effective depth of the beam. Spacing shown here is for general reference only; always follow the project’s structural drawings and local building code.
How the calculation works
cut length = 2(width – 2 × cover) + 2(depth – 2 × cover) + 2 × hook length
hook length = max(6 × bar diameter, 3 in)
total length = stirrups × cut length × (1 + waste%)
- Subtract the end offset from both ends of the member to find the usable length for spacing.
- Divide the usable length by the spacing and add one to get the number of stirrups.
- Subtract twice the concrete cover from the beam width and depth to get the stirrup’s inside leg dimensions.
- Double the sum of the leg dimensions and add two hook extensions for the total cut length of one stirrup.
- Multiply the cut length by the stirrup count, then add the waste allowance to get total rebar length and weight.
Worked example
A 12 ft beam, 12 in wide by 18 in deep, with 1.5 in cover, #4 stirrups, 8 in spacing, and a 2 in end offset:
Usable length: 144 in – 2(2 in) = 140 in. Stirrups: floor(140 / 8) + 1 = 18, and since the last one rounds up to close the run evenly, the actual count is 19 with an adjusted spacing near 7.8 in.
Leg dimensions: 12 – 2(1.5) = 9 in by 18 – 2(1.5) = 15 in. Cut length: 2(9 + 15) + 2(3) = 54 in. Total length: 19 × 54 in / 12 × 1.05 = about 89.8 ft, and at 0.668 lb/ft for #4 bar that is roughly 60 lb of steel.
Before you order
- Spacing and bar size come from the structural drawings, not a general calculator.
- Confirm the hook type (135° seismic hook vs. standard 90°/180°) with your engineer.
- Order in standard stock lengths (20 ft, 40 ft, or 60 ft) and plan cuts to minimize drop waste.
- Check local code for minimum cover requirements before entering a cover value.
Common mistakes
- Forgetting the hook allowance, which understates cut length and rebar orders by 5 in to 8 in per stirrup.
- Using the same spacing across the whole beam when the drawings call for tighter spacing near supports.
- Measuring cover to the outside face of the stirrup instead of to the bar, which throws off leg dimensions.
- Skipping the waste allowance and running short on the last bundle of bar.
Frequently asked questions
How many stirrups do I need for a beam?
Divide the usable length of the beam (total length minus twice the end offset) by the center to center spacing, then add one. A 12 ft beam with a 2 in offset and 8 in spacing needs about 19 stirrups.
What spacing should I use for stirrups or ties?
Spacing is set by the structural drawings or engineer’s design, not by this calculator. Typical ranges run from d/2 near supports to d/4 or tighter in high shear zones, where d is the effective beam depth.
How do I calculate stirrup cut length?
Cut length is roughly twice the sum of the beam width and depth, each reduced by two times the concrete cover, plus two hook extensions of about six bar diameters (minimum 3 in) at each end.
Does this calculator include hook allowance?
Yes. It adds a standard 135° hook extension of six bar diameters per end, with a 3 in minimum, before totaling rebar length.
Should I add extra rebar for waste?
Most estimators add 3 to 8 percent for cut waste, bent bar rejects, and field adjustments. This calculator defaults to 5 percent, and you can change it.