The purpose of your compressor will determine how much pressure you require. Your compressor should only be used for the purpose of inflating cars tires. You will need to have pressures at least 90 PSI, and possibly higher than 110 PSI if you plan on using the portable compressor to power your air tools. Every tool is different and requires different pressures, so make sure you check them before buying an air compressor. You should also check the flow rate of your air compressors, as pressure is just half of what it takes to run an air tool.