Footing Size Calculator
Minimum square isolated footing plan dimensions from column service load and allowable soil bearing capacity. Use this as a quick first estimate before running the full design.
Round up to nearest 50 mm (or 3 in) increment for construction. Verify with full punching shear and flexural design.
Get the full footing design — punching shear check, flexural reinforcement, BBS, and PDF report.
Open Civora App →How to Size an Isolated Footing
The footing plan area is sized from the service (unfactored) loads against the allowable bearing pressure from the geotechnical report. Factored loads are used only for flexural and shear design — not for sizing the plan dimensions.
Formula
A_required = P_service / q_allow
B = √A_required (square footing side)Where P_service includes the column load, the footing self-weight, and the soil overburden above the footing. A common approximation is to take footing self-weight as 5–10% of the column load.
After Sizing
Once the plan dimensions are set, you need to check:
- Punching shear (two-way shear) at d/2 from column face — critical for lightly reinforced flat footings
- Wide-beam shear (one-way shear) at d from the critical face
- Flexural design — cantilever moment from the critical section at the column face
Civora handles all of this automatically and generates the full calculation report and reinforcement drawing.
Full footing design with punching shear and reinforcement.
Full PDF reports, structural drawings (S-01 to S-07), and BBS require a subscription.
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