Enter Pier, Footing, Soil, And Load Data
Use pounds per square foot for area loads, kips for point loads, and inches for concrete dimensions. One kip equals 1,000 pounds.
Example Data Table
| Case |
Area |
Piers |
Footing |
Soil Bearing |
Typical Use |
| Small deck |
120 sq ft |
4 |
30 in round |
2000 psf |
Residential deck posts |
| Porch roof |
180 sq ft |
3 |
36 in round |
1500 psf |
Roof columns |
| Light shed |
240 sq ft |
6 |
30 in square |
2500 psf |
Small accessory building |
Formula used
Area load: load in kips = tributary area × psf ÷ 1000.
Service vertical load: structural service load + footing weight + pier weight + soil cover weight.
Required footing area: required area = service vertical load × 1000 × safety factor ÷ allowable soil bearing.
Average bearing: q = service vertical load × 1000 ÷ footing area.
Edge pressure with moment: qmax = q + M ÷ S, and qmin = q − M ÷ S. Moment is converted from kip-ft to lb-ft.
Uplift: net uplift = uplift demand − dead weight resistance − soil cover − tie-down resistance.
Sliding: sliding margin = vertical load × friction coefficient + passive resistance + anchor shear resistance − lateral demand.
Concrete volume: volume = footing volume + pier volume, then multiplied by the waste allowance.
How to use this calculator
- Enter the project name and tributary area feeding the pier group.
- Add the number of piers sharing the load.
- Enter dead, live, roof, snow, point, uplift, lateral, and moment values.
- Choose the footing and pier shapes.
- Enter concrete dimensions, soil bearing, soil cover, and resistance values.
- Review service load, factored load, bearing pressure, uplift, sliding, volume, and warnings.
- Download the CSV or PDF for job notes and estimating files.
Pier And Footing Design Guide
Concrete piers carry focused loads from posts, decks, porches, sheds, signs, and small buildings. A footing spreads those loads into soil. Good sizing starts with the loads above the pier. It also needs the footing area, concrete weight, uplift, lateral force, and soil bearing value.
A pier can fail in several ways. Soil may be overstressed. The footing may rock under moment. The pier may slide when lateral loads are high. Uplift can pull a light footing from the ground. This calculator checks each issue with service values and simple factored values.
Why Load Balance Matters
The service load shows the real working load. It includes tributary dead load, live load, roof load, snow load, point load, and foundation self weight. The soil check compares average pressure with allowable soil bearing. The moment check estimates maximum and minimum pressure. A negative minimum pressure warns that footing uplift or rocking may occur.
Concrete volume matters during planning. Small piers often need more material than expected. Waste, uneven holes, and bell shaped bottoms add volume. The calculator includes a waste percentage. It also estimates bags for small jobs.
Footing shape affects pressure. A round footing uses circular area. A rectangular footing uses length times width. The calculator also estimates section modulus for moment pressure. This helps you see whether a larger footing is needed.
Important Field Limits
Uplift resistance comes from dead weight, concrete weight, soil cover, and tie down capacity. Wind uplift can exceed these values on open decks and light roofs. Sliding resistance comes from friction and any added passive or anchor resistance. These checks are planning guides only.
Use local code values for soil capacity, frost depth, setbacks, concrete strength, and reinforcement. Soil reports are best for important work. Presumptive soil values can be unsafe when fill, clay, water, or loose sand is present.
It helps compare sizes before drawings, permits, and material orders. Always confirm pier and footing sizes with a qualified professional when loads are high. For best results, measure tributary areas carefully. Separate roof loads from floor loads. Enter conservative soil data. Review every warning line. Increase footing size when bearing, uplift, or sliding demand is close to the limit. Keep clear notes for inspectors before placing concrete in forms safely.
FAQs
What does this pier load calculator check?
It checks service load, factored load, footing pressure, moment pressure, uplift, sliding, concrete volume, and simplified pier compression capacity. It is a planning tool for early sizing and estimating.
Can I use this for a deck foundation?
Yes. It works well for deck planning when loads are known. Use local deck code loads, frost depth, soil capacity, and post spacing. Final sizes should match permit requirements.
What is allowable soil bearing?
Allowable soil bearing is the service pressure soil can support. It is usually given in psf. Use a geotechnical report when available. Presumptive values can be risky on fill or wet soil.
Why does foundation self weight matter?
Concrete and soil cover add downward load. That load increases bearing pressure. It also helps resist uplift. The calculator includes those weights to give a more complete result.
What does negative minimum pressure mean?
Negative minimum pressure means the footing may lift at one edge under moment. This can indicate rocking. A wider footing, deeper embedment, or engineered hold-down may be needed.
How are round and square footings compared?
Round footings use circular area. Square footings use side times side. Rectangular footings use length times width. Each shape also uses its own moment section estimate.
Does this calculator design rebar?
It only estimates minimum steel area and a rough number of #4 bars. Actual reinforcing depends on code, loads, cover, spacing, frost, and construction details.
What is a kip?
A kip is 1,000 pounds of force. Construction load calculations often use kips because pier and footing loads can become large quickly.
Should live load and snow load both be entered?
Enter the values required for your project. Some codes combine loads differently. This calculator lets you control load factors, so you can model the combination you need.
Why include lateral and uplift checks?
Posts and piers may see wind, bracing, slope, or impact forces. Bearing may pass while uplift or sliding fails. These checks help catch those issues early.
Can this replace an engineer?
No. It is for estimating and preliminary sizing. Use a licensed professional for high loads, poor soil, retaining conditions, unusual geometry, public work, or permit-critical designs.