Isolated & Strip Footing module
Free Concrete Footing Calculator — ACI 318-25 Spread (Isolated) and Strip Footings
Design isolated (column) and strip footings per ACI 318-25 with ASCE 7-22 load combinations. Soil bearing (kern-aware or biaxial with partial contact), overturning and sliding, flexural reinforcement with minimum steel, one-way and two-way (punching) shear, bearing at the support and development length.
Free to use with no sign-up: the calculator runs in full in the browser with no account, no trial and no feature limits, and the full detailed calculation is shown on screen, step by step, with the code sections and tables it draws on, so it can be checked by hand. A free account keeps one project in the cloud; unlimited cloud projects and printing the report to PDF are Pro features.
What the calculator includes
- Isolated (column) and strip (wall) footings per ACI 318-25 with the ASCE 7-22 LRFD and ASD combinations, on concrete, steel or wood columns and on concrete, masonry, steel or wood walls, with an optional pedestal and the soil and slab over the footing counted as dead load.
- Load cases of type D, L, Lr, S, R, W and E, each with axial load (negative for uplift), moment and shear in either plane; shear acts through the footing thickness and pedestal height, and the ASCE 7-22 §12.13.4 overturning reduction is a choice.
- Service bearing for every ASD combination, kern-aware or biaxial with partial contact solved by equilibrium, against an allowable adjusted by the geotechnical report's depth and width rules; overturning and sliding safety ratios per combination.
- One-way shear at d, two-way punching per Table 22.6.5.2 with αs for interior, edge and corner columns and moment transfer by shear eccentricity, flexure at the Table 13.2.7.1 section, bearing at the support interface with dowels, and development length per Table 25.4.2.3.
- Rebar minimum and maximum, bar spacing and fy checked as the values are typed, with the f′c minimum for Seismic Design Category D to F flagged.
- Plan and section views for every load case and combination: the punching perimeter, the critical sections, the γs band of a rectangular footing, the bar layers and the kern-aware bearing pressure, with the governing case flagged.
In every StructSuite module
- The code clause behind a value is quoted verbatim beside it from a blue book icon — NDS 2024, SDPWS 2021, AISC 360-22, ACI 318-25, ASCE 7-22 and the 2024 IBC, FEMA P-750 and the I-joist manufacturer's technical bulletins — so the standard does not have to be opened to check it.
- A missing input stops the calculation rather than being filled in silently, and judgment choices start unselected.
- Where a limit applies it is checked as you type: beam RB and column ℓe/d, steel Lc/r, rebar ratios and spacing, fy and f′c.
- Every module prints into one calculation report (Pro) with a cover sheet, a table of contents with measured page numbers and a verification link a plan checker opens without an account.
See the method in a printed report
The sample calculation report (PDF) is a complete StructSuite report printed from the sample project — open it without an account.
Frequently asked questions
Which footing types and checks are included?
Isolated (column) footings and strip footings per ACI 318-25 with ASCE 7-22 load combinations: soil bearing pressure, flexural reinforcement with minimum steel, one-way shear and two-way (punching) shear.
Can I see the calculation steps?
Yes. Each check is shown on screen with the ACI 318-25 section it comes from, and the sample calculation report linked above shows the printed version of the same module.
Which checks does it run?
For every ASD combination: soil bearing (kern-aware, or biaxial with partial contact) against the allowable adjusted by the geotechnical report's depth and width rules, overturning and sliding safety ratios. For every LRFD combination: one-way shear at d, two-way punching shear per ACI 318-25 Table 22.6.5.2 with moment transfer by shear eccentricity, flexure at the Table 13.2.7.1 critical section with minimum and maximum steel, bearing at the support interface with dowels, and development length per Table 25.4.2.3. Every check opens to its derivation.
Is the isolated & strip footing calculator free?
Yes. Free to use with no sign-up: the calculator runs in full in the browser with no account, no trial and no feature limits, and the full detailed calculation is shown on screen, step by step, with the code sections and tables it draws on, so it can be checked by hand. A free account keeps one project in the cloud; unlimited cloud projects and printing the report to PDF are Pro features.