How to use it
- Enter the total load in kilonewtons (kN).
- Enter the soil bearing capacity in kilopascals (kPa).
- Enter the planned footing depth in meters (m).
- Click Calculate to see the required area and width.
This Footings Calculator takes three core inputs—total load, allowable soil bearing capacity, and footing depth—to give you the minimum footing area and a practical width dimension. Knowing the exact area helps you size concrete pours and reinforcement without costly over‑design. The width result translates directly to the plan view, so you can lay out formwork quickly. The tool follows standard engineering practice: larger loads or weaker soils increase area, while deeper footings can reduce required width. Use the output to check compliance with local codes, order materials, and communicate clear dimensions to your contractor.
Pro tips
- Add a 5‑10% waste allowance to the calculated area before ordering concrete.
- Round the width up to the nearest standard formboard size for easier construction.
- If the soil bearing capacity is uncertain, use a conservative value to stay safe.
- Double‑check units: kN for load, kPa for capacity, and meters for depth.
Real-life examples
- A residential builder sizing footings for a new deck.
- A civil engineer verifying foundation size for a small commercial shed.
- A DIY homeowner planning a garden shed on a sloped lot.
Case study
John needed a quick check for his garage foundation. He entered a 150 kN load, 150 kPa bearing capacity, and 0.8 m depth; the calculator returned a 1.25 m² area and a 1.0 m width, letting him order the right amount of concrete and avoid a redesign.