How to use it
- Enter footing width in meters.
- Enter footing thickness in centimeters.
- Provide concrete cover and rebar diameter in millimeters.
- Read the minimum steel area and suggested bar count.
This calculator tells you the smallest steel area your footing needs to meet ACI 318 requirements and translates that area into the number of rebar pieces you should order. Knowing the minimum steel area prevents under‑reinforced footings, which can crack or fail under load. The result appears as mm² for steel area and an equivalent bar count based on the diameter you entered. Use the output to size your order, verify structural drawings, and keep your bid competitive. No guesswork, just the numbers you need to move forward confidently.
Pro tips
- Add a 5‑10% waste allowance when ordering bars.
- Round up the bar count to the next whole bar.
- Choose a standard bar size that meets or exceeds the calculated area.
- Double‑check units: width in m, thickness in cm, cover and diameter in mm.
Real-life examples
- A residential builder sizing footings for a new garage.
- A structural engineer checking reinforcement for a retrofit project.
- A DIY homeowner estimating rebar for a garden retaining wall.
Case study
John, a small‑contractor, entered a 3 m width and 40 cm thickness and saw the calculator recommend at least 0.216 mm² steel, which equated to a single 12 mm bar. He ordered exactly that, avoided excess material, and finished the footing on schedule.