bieng a mechanic, i have a 20 at home, for, i dont even know, cause i hate workin much anything anymore, but a sander , is a continuosly running tool, different from air tools i use, enclosed is some useful information, i hope, first is home use, second is business use
Home Use
Compressed-air power tools can dramatically decrease the amount of time spent on a project. Many homeowners will use smaller, portable units (either hand-carried or wheeled) that move easily from the garage to the house, yard or roof. Common air tools such as brad nailers, reversible drills, and impact wrenches require about 0–5 CFM (Cubic feet per minute — units in which air flow is measured). It's important to know if the compressor you purchase will drive the air tool you'll need for your project. For example, smaller air nailers run on 2 to 5 CFM at 70 to 90 PSI, while larger shears, sanders and polishers require up to 10 or more CFM and 100 to 120 PSI.
Business Use
Air compressors used for business/professional applications are often classified “industrial grade.” They're packed with features that let you take on more demanding jobs with more horsepower, more CFM, more PSI and more (longer) run times. Though some industrial-grade compressors are portable, many are stationary units with large-capacity, ASME certified air tanks (up to 120 gallons), greater HP, more CFM air volume and faster recovery time to run a wide variety of air tools for as long as you need them to do the job.
heres some way to figure, based on specs of your tools u will be using
How do I determine my CFM Requirements?The chart below includes some common air tools and their average CFM measurements. Reference this chart to determine what continuous CFM rating is required of your air compressor. Air tools are often rated as “Average CFM.” “Average CFM” is typically based on a 25% duty cycle (15 seconds out of a min.). This sometimes creates a problem with tools that are used on a continuous basis (ex. orbital sanders, die grinders, etc). Nailers and impact wrenches typically don't have the same problem since by their nature are used more intermittently.
If you plan on using an air tool on a continuous basis, it is a good idea to multiply the “Average CFM” x 4 to get a continuous CFM rating for the tool.