GEOTECHNICAL
Foundation Design Calculator
Isolated · Combined · Strip · Raft · Soil bearing · Reinforcement
qall
Pu
Af
Isolated footing design
kN
×
mm
kN/m²
MPa
MPa
Footing area required
—
m²
Footing size (Bf × Lf)
—
m
Effective depth (d)
—
mm
Steel area required
—
mm²
Net pressure (qnet)
—
kN/m²
Af = Pu / qall | Bf = √Af
Footing geometry
Isolated footing — square or rectangular
Design checks
Bearing pressure
✓ OK
Punching shear
✓ OK
Bending moment
✓ OK
Steel ratio
✓ OK
Combined footing
kN
kN
m
kN/m²
Total load (Ptotal)
—
kN
Resultant location
—
m from P₁
Footing length (Lf)
—
m
Footing width (Bf)
—
m
Ptotal = P₁ + P₂ | x̄ = (P₁·0 + P₂·L) / Ptotal
Combined footing
Combined footing — resultant at centroid
Strip footing (wall)
kN/m
kN/m²
mm
Required width (B)
—
m
Projection each side
—
mm
Effective depth
—
mm
Steel per meter
—
mm²/m
B = w / qall | projection = (B − tw) / 2
Strip footing
Strip footing for load-bearing walls
Raft foundation
kN
×
m
kN/m²
Average pressure
—
kN/m²
Status
—
—
Area required
—
m²
Actual area
—
m²
q = Ptotal / (L × B) | q ≤ qall
Raft layout
Raft foundation — uniform pressure distribution
Soil bearing capacity
type
m
m
—
Ultimate bearing capacity
—
kN/m²
Safe bearing capacity
—
kN/m²
Factor of safety
—
—
Soil classification
—
—
qu = c·Nc + γ·Df·Nq + 0.5·γ·B·Nγ
Bearing capacity
Ultimate vs safe bearing capacity