Soil Bearing Capacity Estimator

How It Works

1. Select a Bearing Prompt

   Choose a local IBC-style row or enter a custom allowable bearing value from current project geotechnical or AHJ-reviewed documents. The app does not classify the soil for you.

2. Enter Service Load

   Input the vertical service load assigned to this footing. The calculator divides load by allowable bearing to find the required bearing area: A = P / q_allowable.

3. Review Local Pressure

   Design mode reports rounded square or 2:1 rectangular dimensions and utilization of the selected local prompt. Check mode compares an entered existing footing area with that same prompt.

4. Carry the Source Gaps

   Use the warnings list to verify missing items such as settlement, groundwater, self-weight, overburden, frost, eccentricity, shear, flexure, reinforcement, adopted code, and AHJ review.

Built For

• Early footing bearing-area scoping before project-specific geotechnical review
• Comparing local presumptive-row prompts with a custom geotechnical allowable value
• Checking whether an entered existing footing pressure is above a local planning prompt
• Documenting source gaps before structural footing design, rebar checks, or permit review
• Screening deck, shed, post-frame, or light commercial concepts before qualified review
• Preparing questions for a geotechnical engineer, structural engineer, contractor, inspector, or AHJ

Features & Capabilities

Local IBC-Style Prompts

Five local presumptive bearing rows are retained as screening prompts with source warnings, plus a custom geotechnical input.

Bearing-Area Arithmetic

Computes required area from entered service load and selected allowable bearing prompt, then rounds dimensions to even inches.

Existing Footing Calculator

Compares entered existing footing area with the selected prompt and labels below, near, or above the local prompt without approval verdicts.

Square and Rectangular Options

Shows square footing prompts or a simple 2:1 rectangular length-to-width prompt for early comparison.

Visible Source Gaps

Keeps geotechnical, settlement, groundwater, frost, load, self-weight, overburden, eccentricity, structural, code, and AHJ gaps visible.

PDF Export

Export the calculator output with source warnings and references for project notes, not as permit-ready construction documents.

Assumptions

• Preset bearing rows are local IBC-style prompts, not site soil classification or code approval
• Applied load is entered by the user and should already include the project load basis required for the review
• Design mode uses A = P / q_allowable and rounds square or 2:1 rectangular prompts up to even inches
• Check mode compares entered existing footing area against the selected prompt and reports a review tier
• Custom bearing input should come from current geotechnical, structural, code, or AHJ-reviewed documents
• No footing self-weight, overburden, groundwater, settlement, frost, surcharge, eccentricity, lateral load, shear, flexure, or reinforcing checks are computed

Limitations

• Does not classify soil, approve fill, verify compaction, or replace borings, testing, proof roll, or geotechnical recommendations
• Does not perform settlement, consolidation, expansive-soil, liquefaction, scour, frost, groundwater, slope, or erosion analysis
• Does not generate ASCE 7 load combinations or validate tributary area, load path, dead/live/roof/snow/wind/seismic loads
• Does not evaluate footing self-weight, soil overburden, surcharge, adjacent excavations, buoyancy, uplift, eccentricity, sliding, or overturning
• Does not design concrete thickness, one-way shear, punching shear, flexure, rebar, dowels, development, cover, drainage, or frost protection
• Does not determine adopted-code compliance, permit readiness, inspection outcome, insurer acceptance, or AHJ approval
• Does not authorize construction without qualified structural, geotechnical, contractor, inspector, and AHJ review

References

• ICC IBC Chapter 18 source pointers for soils, foundations, and presumptive bearing context
• ASCE 7 source pointer for structural loads and load-combination context
• USDA NRCS Web Soil Survey source pointer for soil-information context only
• DOE/ORNL Building Foundation Handbook source pointer for foundation moisture and building-science context
• CRSI shallow-foundation checklist source pointer for structural follow-up context
• NIST SP 811 Appendix B.8 unit-conversion source pointer

Frequently Asked Questions