> ## Documentation Index
> Fetch the complete documentation index at: https://calcs.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Design a Pier Footing to ACI 318-14

> Design pier and deck footings to ACI 318-14 (IBC 2018). An earlier code edition, kept for existing projects.

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    <div className="calc-details-head"><span className="calc-card-icon"><Icon icon="calculator" size={20} color="#0076d6" /></span><p className="calc-details-name">Pier Footing (ACI 318-14)</p><a className="calc-details-run" href="https://app.calcs.com/new/sheet/foundationsPierFootingUSA">Run the calc</a></div>
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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.
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<Note>
  This calculator uses an earlier code edition (IBC 2018). It stays available for existing projects. For new designs, check the [Calculator Library](/docs/calculators/us) for the current edition.
</Note>

## Method & scope

| Property         | Detail                                                                                                                                                                         |
| ---------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| Design standards | IBC 2018                                                                                                                                                                       |
| Regions          | United States                                                                                                                                                                  |
| What it checks   | Vertical bearing capacity, Lateral soil resistance (IBC 2018, Cl. 1807.3), Concrete compression and bending capacity (ACI 318-14, Ch. 21), Shear capacity (ACI 318-14, Ch. 21) |

#### 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.

## How to use it

<Steps>
  <Step title="Open the calculator">
    Open it from **Run calc** in the About this calculator panel above.
  </Step>

  <Step title="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](/docs/running-calculations/checking-results/checks-references-conditions-assumptions).
  </Step>

  <Step title="Review the results and export">
    Check the utilization of each governing check in the summary, then export a PDF report. See [Views and Export](/docs/running-calculations/exporting-reports/views-and-export).
  </Step>
</Steps>

## Common questions

<AccordionGroup>
  <Accordion title="What design standard does this calculator use?">
    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 (phi*Mn, phi*Vn) for both bending and shear. Bearing pressure is checked against allowable capacity under service loads.
  </Accordion>

  <Accordion title="What are the key inputs?">
    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.
  </Accordion>

  <Accordion title="What does the calculator check and output?">
    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.
  </Accordion>

  <Accordion title="Can I use this for deck post footings and residential columns?">
    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.
  </Accordion>

  <Accordion title="How does load linking work for pier footings?">
    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.
  </Accordion>

  <Accordion title="Can I link this footing directly to a column or deck post calculation?">
    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.
  </Accordion>
</AccordionGroup>

## Next steps

<CardGroup cols={2}>
  <Card title="Calculator Library" icon="list" href="/docs/calculators/us">
    Complete list of Calcs.com design calculators available for United States projects (AISC, ACI, NDS, ASCE 7, IBC, and related standards).
  </Card>

  <Card title="Design a Wall Footing to ACI 318-19" icon="calculator" href="/docs/calculators/us/foundations-and-retaining-walls/foundationsWallFootingUSAACI318-19">
    Design continuous wall footings to ACI 318-19 per IBC 2021 or IBC 2024. Results cover ultimate load, bearing capacity and serviceability.
  </Card>

  <Card title="Design a Wall Footing to ACI 318-14" icon="calculator" href="/docs/calculators/us/foundations-and-retaining-walls/foundationsWallFootingUSA">
    Design continuous wall footings to ACI 318-14. An earlier code edition, kept for existing projects.
  </Card>

  <Card title="Design a Wood Column (ASD) to NDS 2018" icon="calculator" href="/docs/calculators/us/columns/timberColumnASD">
    Design wood columns and studs to NDS 2018 (ASD). An earlier code edition, kept for existing projects.
  </Card>
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