# How to calculate footing loads > A footing carries the column above it plus its own weight. Here is how to find the load for bearing and for footing strength, using service and factored values. **Category:** Load paths **Author:** Elena Marchetti (Structural engineer ยท Founder) **Published:** 2026-05-12 --- A footing carries the column above it plus its own weight, and it is where a load takedown finally lands. To find the footing load, take the column reaction at the base of the building, then add the self weight of the column and the footing. You then use the service value to size the footing against the soil and the factored value to design the footing's strength. StructLoads gives the base column reactions; this page turns them into footing loads. ## What sits on a footing A [shallow foundation](https://en.wikipedia.org/wiki/Shallow_foundation) under a column carries three things: the accumulated column reaction from every floor above, the self weight of the column itself, and the self weight of the footing and any soil on it. The column reaction is by far the largest, and it comes straight from the bottom of a [structural load takedown](/blogs/how-to-do-a-structural-load-takedown). The other two are small additions you must not forget, in line with general [foundations](https://www.designingbuildings.co.uk/wiki/Foundations) guidance. ## Two loads for two checks A footing is checked two ways, and each uses a different version of the load. | Check | Load to use | Compared against | | --- | --- | --- | | Footing plan size | Service load | Allowable soil bearing pressure | | Footing strength | Factored load | Concrete and reinforcement capacity | Sizing the plan area is about the real pressure the soil feels, so it uses the service [load](https://en.wikipedia.org/wiki/Structural_load). Designing the footing's thickness and bars is a strength check, so it uses the factored load. You therefore carry both values down, as in [factored loads vs service loads](/blogs/factored-loads-vs-service-loads). You can watch the split play out in [StructurePoint's spread footing worked example](https://structurepoint.org/publication/pdf/Reinforced-Concrete-Square-Spread-Footing-Analysis-Design-ACI318-14.pdf), which sizes the base from the 400 kip dead and 270 kip live service loads against the allowable pressure, counting the fill and basement floor sitting on the footing, and only then applies the factored ACI 318 combinations for the punching shear, one-way shear and flexure checks. ## Sizing the footing from the service load Divide the service load by the allowable soil bearing pressure to get the required plan area. Take a column with about 819 kN of service reaction, add roughly 30 kN for the column and footing self weight, giving about 850 kN. On soil with an allowable bearing pressure of 200 kPa, the required area is 850 divided by 200, which is about 4.25 square metres, so a footing of roughly 2.1 by 2.1 metres. The allowable pressure comes from a geotechnical assessment, not a guess. ## Designing the strength from the factored load The footing's own thickness and reinforcement are designed for the factored load, about 1070 kN in the worked column from [how to calculate column loads](/blogs/how-to-calculate-column-loads), plus the factored self weight. That factored load drives the punching shear and bending checks of the footing, which set its depth and bars. The plan size and the strength design therefore use different load values on the same footing, which is the point to keep straight. ## A common mistake The frequent error is to use one load for both checks. Sizing the plan area on the factored load oversizes the footing, because the soil never feels the factored value; designing the strength on the service load undersizes the reinforcement. Keep the service load for bearing and the factored load for strength, and the footing is both safe and economical, the same discipline used when [sizing a column from axial load](/blogs/how-to-size-a-column-from-axial-load). ## Key takeaways: footing loads A footing load is the base column reaction plus the column and footing self weight. Size the plan area on the service load against the allowable bearing pressure, and design the strength on the factored load. The column reaction comes from the takedown; the soil pressure comes from geotechnical advice. StructLoads supplies the base reactions as a preliminary figure that a qualified engineer and a geotechnical assessment confirm. ## Quick answers ### How do you calculate the load on a footing? Take the column reaction at the base of the building from a load takedown, then add the self weight of the column and the footing. Use the service load for sizing the footing plan area against the allowable soil bearing pressure, and the factored load for designing the footing's reinforcement and thickness. The takedown gives the column reaction that starts it. ### Do you use service or factored loads for a footing? Both, for different checks. Sizing the footing plan area against the allowable soil bearing pressure uses service loads, because bearing is a check on real pressure. Designing the footing's own strength, its thickness and reinforcement, uses factored loads. So you carry both the service and the factored column reaction down to the footing. ### How do you size a footing from its load? Divide the service load by the allowable soil bearing pressure to get the required plan area, then choose dimensions at least that large. For an 850 kN service load on soil allowed 200 kPa, the area is about 4.25 square metres, so roughly a 2.1 by 2.1 metre footing. The strength design of thickness and bars then uses the factored load. ### When is a hand footing load not enough? A hand footing load is a preliminary gravity figure. It is not enough when there are moments or uplift, eccentric or combined footings, lateral loads, or difficult ground needing a geotechnical assessment. In those cases the bearing pressure is not uniform and settlement and stability govern. Use the hand load to size the early footing, then full design with a qualified engineer.