Input values
Calculate a Cylinder Footing Load
Use SI units. Enter an allowable bearing pressure from a geotechnical source, not an ultimate soil capacity.
Worked reference
Example Data Table
| Input or result | Example value | Meaning |
|---|---|---|
| Footing diameter | 1.80 m | Circular contact width. |
| Footing thickness | 0.60 m | Cylinder height used for volume. |
| Column service load | 220 kN | Applied vertical reaction. |
| Concrete density | 2400 kg/m³ | Used to calculate footing self-weight. |
| Allowable bearing pressure | 150 kPa | Approved soil pressure limit. |
Calculation method
Formula Used
A = π × D² ÷ 4Contact area of the circular footing.
V = A × tConcrete volume of the cylindrical footing.
Wf = V × (ρc × 9.80665 ÷ 1000)Footing self-weight in kilonewtons.
Pgross = Pcolumn + Padditional + WfTotal vertical service load before soil displacement.
qgross = Pgross ÷ AGross contact pressure at the bearing surface.
Qallow = A × qallow × (1 − r ÷ 100)Reduced allowable load used for the displayed bearing check.
Here, D is diameter, t is thickness, ρc is concrete density, and r is the selected capacity reduction. Net pressure subtracts estimated displaced soil weight before dividing by area.
Practical steps
How to Use This Calculator
- Enter the cylinder diameter and concrete thickness in metres.
- Enter the column service load and any attached permanent load.
- Provide realistic concrete density and local soil unit weight values.
- Enter allowable bearing pressure from the project geotechnical information.
- Use capacity reduction only as an additional preliminary allowance.
- Select Calculate Footing Load and compare gross pressure with effective allowable pressure.
- Download, print, or record the result with your design assumptions.
Foundation planning
Cylinder Footing Load Considerations
Load Path and Contact Area
Cylinder footings spread concentrated loads across a circular soil contact area. Their round shape suits columns, poles, tanks, signs, and isolated supports. A reliable check begins with the service load. Add the supported load, attached dead loads, and footing self-weight. This gives the gross vertical load transferred to the ground.
The circular base area controls bearing pressure. A larger diameter creates more contact area. More area lowers pressure for the same load. Thickness affects concrete volume and self-weight. It may also affect structural strength. This calculator evaluates the geotechnical bearing side only. A qualified designer must still check bending, punching shear, reinforcement, and local code requirements.
Weight and Soil Displacement
Concrete density converts footing volume into a useful self-weight estimate. The calculator uses standard gravity for this conversion. Soil unit weight and excavation depth estimate the soil removed from the footing location. Subtracting that removed soil weight produces a net load estimate. Gross pressure remains the conservative value for many early sizing studies.
Capacity and Ground Conditions
Allowable bearing pressure often already includes a safety margin. Enter the project value from a geotechnical report. The capacity reduction input provides an additional planning allowance for uncertain conditions. It lowers the entered allowable pressure before comparison. Do not use it to replace professional judgment. Water, loose fill, frost, nearby excavation, and variable strata can change capacity.
Limits of a Bearing Check
A passing pressure result does not prove the footing is adequate. Settlement can govern on compressible soil. Eccentric column loads may cause nonuniform contact pressure. Lateral loads can create overturning and sliding concerns. Deep foundations, grade beams, or larger footings may be needed when these conditions are important.
Reading the Results
Use consistent SI units throughout the calculation. Diameter, thickness, and excavation depth use metres. Loads use kilonewtons. Bearing pressure uses kilopascals, which equal kilonewtons per square metre. Review the result panel carefully. A low utilization indicates available bearing reserve. A result above one hundred percent requires a larger base, lower load, better soil, or a redesigned foundation.
Documentation and Review
Record assumptions with the project calculations. Keep the geotechnical report, column reactions, concrete specification, and site observations together. Recheck dimensions when plans change. This simple workflow supports fast comparisons during preliminary construction planning. Final footing design should be reviewed and approved by the responsible engineer before field work starts. It helps teams communicate preliminary loading assumptions before detailed design.
Common questions
Cylinder Footing Load FAQs
1. Which loads does this calculator include?
It combines the column service load, added permanent load, and calculated concrete self-weight. It also estimates displaced soil weight for the net load result.
2. Is gross bearing pressure the same as allowable bearing pressure?
No. Gross bearing pressure is the calculated ground contact pressure. Allowable bearing pressure is the project limit supplied by geotechnical design information.
3. Why does the calculator show net pressure?
Net pressure recognizes the weight of soil removed during excavation. It can help compare replacement footing weight with the original overburden pressure.
4. Can I enter ultimate soil bearing capacity?
No. Use an allowable bearing value unless your selected design standard clearly permits a factored resistance method and matching load combinations.
5. Does a passing bearing result prove the footing is complete?
No. Structural checks remain necessary. Review bending, punching shear, reinforcement, settlement, sliding, uplift, overturning, and code-required load combinations.
6. Which units should I use?
Enter metres for geometry, kilonewtons for load, kilograms per cubic metre for density, and kilopascals for bearing pressure.
7. How does concrete density affect the result?
Higher density increases footing self-weight. This raises gross load and contact pressure, especially for thick or large-diameter footings.
8. Where are cylinder footings commonly used?
They are often used below round columns, light poles, sign supports, tanks, equipment supports, and other isolated circular loads.
9. What should I do if utilization exceeds 100 percent?
Increase the footing diameter, reduce applied load, improve the foundation level, use better ground, or ask an engineer to redesign the support system.
10. Do groundwater conditions matter?
Yes. Water can alter soil unit weight, effective stress, settlement behaviour, and construction conditions. Use project-specific geotechnical guidance where groundwater is present.
11. Is professional review needed before construction?
Yes. Professional review keeps the foundation safe, compliant, and durable.