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Pier Footing (ACI 318-14)

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Pier footing loads link to the column or deck post above, so load changes propagate downstream automatically. Design pier and deck footings to ACI 318-14 (IBC 2018). Results cover bearing capacity under service loads, flexural design, and one-way and two-way (punching) shear.
This calculator uses an earlier code edition (IBC 2018). It stays available for existing projects. For new designs, check the Calculator Library for the current edition.

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Method & scope

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Calculation method

The Pier Footing (ACI 318-14) calculator designs cylindrical plain concrete pier footings per ACI 318-14, referenced by IBC 2018 (ASCE 7-16 load combinations). It checks vertical bearing capacity, lateral soil resistance for embedded posts, concrete compression and bending capacity, and shear.
Vertical bearing capacity
Service axial load P_s from ASD load combinations is compared to the allowable vertical bearing capacity q_a: utilization = q_s / q_a ≤ 1.0 Where q_s = P_s / A_g (gross bearing area of the pier base).
Lateral soil resistance (IBC 2018, Cl. 1807.3)
For embedded piers resisting lateral loads, the IBC 2018 method is used. Allowable lateral soil stress S_a is calculated as a function of embedment depth (limited to 12 ft maximum for the formula). For unconstrained piers, the required embedment depth d is determined from the applied lateral force V_s and moment M_s: S’_1, lateral soil stress at 1/3 of embedment depth S’_3, lateral soil stress at embedment depth The calculator notes that the IBC equation for unconstrained embedded posts does not handle moment loads rigorously and embedment depth varies based on assumptions.
Concrete compression and bending capacity (ACI 318-14, Ch. 21)
The pier is checked for combined compression and bending under the governing LRFD load combination. The interaction check compares the maximum of two demand-to-capacity ratios:
  • Bending governs: (M_u,max / S_m, P_u,min / A_g) / (phi × 5 × lambda × f’_c × shear area)
  • Compression governs: M_u,max / (phi × M_n,comp) + P_u,max / (phi × P_n)
utilization = max(interaction ratio) ≤ 1.0
Shear capacity (ACI 318-14, Ch. 21)
Shear demand V_u is compared to the plain concrete shear strength: phi × V_n = phi × 2 × lambda × sqrt(f’c) × (A_n / 2) utilization = V_u / (phi × V_n) ≤ 1.0
Assumptions
Post is centered on the footing. The pier is prismatic unreinforced concrete. Skin friction on the pier sides is ignored, only pure end bearing is considered. The pier is assumed continuously restrained against buckling by surrounding soil, so unbraced length terms are omitted from compression capacity. Development length and deflection checks are performed separately.

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How to use it

1

Open the calculator

Open it from Run calc in the About this calculator panel above.
2

Enter your inputs

Work through the input sections from top to bottom. Click any input label to see its reference explanation, clause, conditions and assumptions. See Checks, References, Conditions and Assumptions.
3

Review the results and export

Check the utilization of each governing check in the summary, then export a PDF report. See Views and Export.

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Common questions

The calculator applies ACI 318-14 for reinforced concrete section design per IBC 2018 load combinations (ASCE 7-16). Strength design (LRFD) is used, factored loads are checked against reduced design capacities (phiMn, phiVn) for both bending and shear. Bearing pressure is checked against allowable capacity under service loads.
Key inputs are footing plan dimensions (square or rectangular), footing depth, column or pier diameter, concrete compressive strength (f’c), reinforcement bar size and spacing, concrete cover, allowable bearing pressure, and applied column loads (axial, moment, shear). Loads can be entered manually or linked from a column or deck post calculation above.
Checks include: bearing pressure under service loads versus allowable soil bearing capacity, flexural reinforcement in both plan directions at the face of the column, one-way shear (wide beam) at d from the column face, and two-way (punching) shear at the critical perimeter around the column. Required reinforcement area and utilization ratios are reported for each check.
Yes. The calculator is suited to residential and light commercial pier footings for both structural columns and deck posts. For deck posts, enter the deck post base reaction (typically from a beam calculation above) as the applied axial load and set moment to zero for concentric loading. The calculator returns the minimum footing size for the given bearing capacity.
Column axial force and moment link directly from a column calculator in the same Calcs.com project. When column loading or height changes, the footing rechecks bearing pressure, flexure, and shear automatically. For deck projects, linking post reactions from the deck beam calculator ensures the footing design stays current through the full load path.
Yes. The applied axial force and moment at the column base link automatically from a connected column calculator. Change the column section, height, or tributary load, and the pier footing recalculates immediately, bearing pressure, flexure, one-way shear, and punching shear all update without manual re-entry.

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Next steps

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