Cells integrate endogenous and exogenous mechanical forces to sense and respond to environmental signals. In particular, cell-generated microscale traction forces regulate cellular functions and impact macroscale tissue function and development. Many groups have developed tools for measuring cellular traction forces, including microfabricated post array detectors (mPADs). mPADs are a powerful tool that provides direct traction force measurements through imaging post deflections and utilizing Bernoulli-Euler beam theory. In this technical note, we investigated how mPADs presenting two different top surface areas but similar effective stiffness influence cellular spread area and traction forces for murine embryonic fibroblasts and human mesenchymal stromal cells. When focal adhesion size was restricted via mPAD top surface area, we observed a decrease in both cell spread area and cell traction forces as the mPAD top surface area decreased, but the traction force-cell area linear relationship was maintained, which is indicative of cell contractility. We conclude that the mPAD top surface area is an important parameter to consider when utilizing mPADs to measure cellular traction forces. Furthermore, the slope of the traction force-cell area linear relationship provides a useful metric to characterize cell contractility on mPADs.