Subfootprint variability (SFV), or representativeness error, is variability within the footprint of a satellite that can impact validation done by comparison of in situ and remote sensing data. This study seeks to determine the size of the SFV as a function of footprint size in two regions that were heavily sampled with in situ data. The SPURS-1 (Salinity Processes in the Upper-ocean Regional Studies) experiment was conducted in the subtropical North Atlantic in 2012-2013, whereas the SPURS-2 study was in the tropical eastern North Pacific in 2016-2017. SFV was also computed using a high-resolution regional model based on ROMS (Regional Ocean Modeling System). We computed SFV at footprint sizes ranging from 20-100 km for both regions. SFV is strongly seasonal, but for different reasons in the two regions. In the SPURS-1 region, the meso- and submesoscale variability seemed to control the size of the SFV. In the SPURS-2 region, the SFV is much larger than SPURS-1 and controlled by patchy rainfall.