Calculate ultimate and allowable bearing capacity of strip, square, and circular shallow foundations using Terzaghi, Meyerhof, and Hansen geotechnical theories.
Formula and method
Terzaghi shallow-foundation bearing capacity combines cohesion, surcharge, and self-weight terms with shape factors for rectangular footings.
q_{ult} = c N_c s_c + q N_q + 0.5 \gamma B N_\gamma s_\gamma
Convert friction angle φ to Terzaghi factors Nc, Nq, and Nγ.
Apply shape factors sc and sγ based on footing B/L ratio.
Compute ultimate bearing pressure q_ult from cohesion, overburden q = γ·Df, and footing width B.
Divide by the safety factor (typically 3.0) to obtain allowable bearing capacity.
Frequently asked questions
What is Terzaghi's bearing capacity equation?
qult = c·Nc·sc + q·Nq + 0.5·γ·B·Nγ·sγ, where c is cohesion, q is overburden pressure, γ is soil unit weight, B is footing width, N factors depend on friction angle, and s factors account for footing shape.
What soil parameters are needed?
You need the soil cohesion (c), friction angle (φ), unit weight (γ), footing depth (Df), footing width (B) and length (L), and a safety factor (typically 3.0 for bearing capacity).
How is the allowable bearing pressure determined?
The ultimate bearing capacity qult is divided by the safety factor to obtain the allowable bearing pressure qallow. This is the maximum safe loading the soil can support without shear failure.
Related Calculators & Tools
Retaining Wall Earth Pressure CalculatorCalculate active and passive lateral earth pressure distributions and overturning moments on retaining walls using Rankine and Coulomb geotechnical equations.
Concrete Volume CalculatorCalculate concrete volume and required cement bags, sand weight, and aggregate for slabs, footings, and columns with custom mix ratios and waste factors.
Rebar Quantity & Weight CalculatorCalculate total rebar segment lengths, weight per bar size, overlap lap splices, and spacing counts for concrete slabs, beams, and columns with CivilMath.
Brick Wall & Mortar Quantity CalculatorEstimate the number of standard bricks, mortar volume, and dry cement-sand quantities for single or double-wythe brick masonry walls with waste margins.
Concrete Slab Cost CalculatorFree concrete slab cost calculator. Enter slab or pad dimensions and your local ready-mix price to estimate concrete volume, total material cost, and price per square foot.
Calculations are preliminary estimates for planning and education.
Verify results against project documents and applicable codes with a licensed Professional Engineer.
The interactive calculator loads automatically when JavaScript is available.