Air Compressor Size Chart And Selection Guide

An air compressor is a special mechanical device that increases a specific gas pressure by increasing the volume, just like a pump does. The wrong air compressor size can lead to pressure transients leading to very high energy costs and maintenance of the component and eventually cost an individual or business millions of dollars per year.

To maintain and use efficient air compressor systems, it is inevitable to account for the size and type of air compressor and that is where an air compressing size chart and selection guide comes in.

Air Compressor Size Chart: Important Measurements 

There are a couple of measurements that are utilized to determine the air compressing size or simply the size of an air compressor.  Let’s look at some of the key measurements as follows; 

Cubic feet per minute

The first measurement should be the CFM, which stands for cubic feet per minute. This measurement is arrived at by calculating the area then substituting the fpm(feet per minute) with the cubic feet value after it is squared. The CFM determines the size of an air compressor that is most suitable. 

Pressure measurement

Another significant measurement to take is the pressure measurement. Too much pressure can, unfortunately, lead to a deadly and costly mistake and suddenly drive the compressor into a surge. It can cause equipment ruin, high repair costs. It can also be a health risk for the workers involved.

If you are working with a heavy machine, it would be advisable to go for a high-pressure compressor as opposed to a low-pressure compressor.

Duty cycle

Another important item worth considering is the Duty cycle. In air compressing, the term duty cycle refers to the time it takes for an air compressor pump to completely fill the tank with air. This means, how often the compressor will be cycling on and off while pumping.

The Duty cycle percentage is calculated by the use of the compressor time (time on + time off) at a particular pressure. It’s important to understand the units of measurements well in order to efficiently work with an air compressor. The measurements are mostly based on cubic meters.

Air Compressing Size Chart: Determining CFM Requirements

Use the chart below to determine the level of continuous CFM rating you need for your air compressor. Important to note that air tools are normally rated as  “Average CFM.” This average is based on one-quarter of a duty cycle. This can create challenges for tools that are continually at work such as air grinders, and orbital sanders. 

If your tool is for continuous use, then please make a point of multiplying by 4 the Average CFM” to get the correct CFM rating. 

Air Tool Average CFM @ 90 PSI
Speed Saw5
Orbital Sander6-9
Angle Disc Grinder – 7″5-8
Brad Nailer0.3
Chisel/Hammer3-11
Cut-Off Tool4-10
Dual Sander11-13
Framing Nailer2.2
Hydraulic Riveter4
Needle Scaler8-16
Nibbler4
Mini Die Grinder4-6

Here is a more elaborate chart of air requirements for common pneumatic tools

Please note that this chart serves as a guide only, based on different brands’ 

ToolCFM @ LoadRecommended CFM
Wrenches  
3/8″ Impact Wrench 1/2″ Impact Wrench 3/4″ Impact Wrench8-36 9-42 9-5530-40 CFM 30-40 CFM 30-40 CFM*
1″ Impact Wrench9-10260-70 CFM*
#5 Spline Impact Wrench60-95100 CFM
Ratchets  
1/4″ Ratchet 1/2″ Ratchet3/8″ Ratchet10-20 15-2311-2430-40 CFM 30-40 CFM30-40 CFM
Drills  
1/2″ Drill 3/8″ Drill17-35 13-4430-40 CFM 30-40 CFM
Grinders  
1/4″ Die Grinder6-4030-40 CFM
Angle Grinders (5″)Vertical Grinder16-7650-9360-70 CFM60-70 CFM
Sanders  
Tire Buffer Orbital Sander13-15 14-2230-40 CFM 30-40 CFM
Polishing Sander22-3960-70 CFM
Percussive  
Air Hammer (Zip Gun)Scalers Engraving Pens7-304-15 1-530-40 CFM30-40 CFM 30-40 CFM
Reciprocating Saw6-5160-70 CFM
Walk Behind Saw90-92100 CFM
Concrete  
Clay Digger 30/35 lb. Pavement Breaker 60 lb. Pavement Breaker36-47 48-52 64-7060-70 CFM 60-70 CFM 60-70 CFM
90 lb. Pavement Breaker62-85100 CFM

Air Compressor Sizing & Selecting 

Check out the charts below for service shop tools and body shop tools

Body Shop Tools

How ManyType of ToolCFM SingleCFM Total
N/AImpact Wrench, 1/2″ Drive3N/A
2Impact Wrench, 3/4″ Drive714
2Impact Wrench, 1″ Drive1020
2Tire Changer w/Inflator48
2Grease Gun48
1Oil Pump44
1Parts Washer ( Air-agitated)22
4Lift (in-ground) 8000 lbs ( Add 1 CFM for each additional 1000 lbs.)624
N/AAir Jack4N/A
N/ACabinet Blaster w/5/64 Nozzle7N/A
N/ACabinet Blaster w/1/8 Nozzle15N/A
N/ACabinet Blaster w/5/32 Nozzle20N/A
N/AOther Tools/EquipmentN/AN/A
 Total CFM in Service Shop80 

Service Shop Tools

How ManyType of ToolCFM SingleCFM Total
N/A“DA ” Sander12N/A
N/A6″ Grinder10N/A
N/APanel Cutter8N/A
N/APlasma Cutter6N/A
N/ASpray Gun, Touch-up4N/A
N/ASpray Gun, Professional9N/A
N/ASpray Gun, HVLP11N/A
N/APaint Shaker3N/A
N/ARespirators (Per Man)4N/A
N/AOther Tools/EquipmentN/AN/A
 Total CFM in Service ShopN/A

How to determine the maximum air pressure

This is the formula used to calculate the maximum air pressure for an air compressor 

Maximum pressure = Tank volume in cubic feet multiplied by standard pressure during one cycle, multiplied again by cranks per minute.

That is, Maximum pressure = Tank volume X Standard pressure X Cranks per minute

To achieve accurate results, begin by converting the capacity of the tank to cubic feet from cubic meters. Next, start up the air compressor, take measurements of the load and unload cycles on the tank gauge. With the help of a stopwatch, note how long it takes from the second the compressor begins running to the time it stops. If the compressor has been off, fill the tank to the maximum first before you start recording.

Hey, come on now. Please don’t be intimidated by this formula, you absolutely need not memorize anything whatsoever especially if intense calculations are not your cup of tea! Of course, it is in such situations that our good air compressing size chart comes in.  So you can now breathe a sigh of relief, forget about this weird maths and look up at the chart to help you select the most suitable air compressing device according to your needs. 

Air compressor Selection Guide

There are various things you need to think about before you finally select the air compressing system that works best for you. For example,  you need to analyze the volume and inlet pressure that you require. If your compressing needs are based on heavy-duty tools, you will require a compressor with maximum air pressure depending on the energy consumption.

It is also important that you get to understand different air compressor types. For instance, piston type compressors rely on a special motor that builds up new air pressure when the existing pressure gets finished. They keep running continuously to deliver a consistent air flow rate. The pressure in two-stage compressors on the other hand should always be greater than the atmospheric pressure for proper function. The two-stage compressor works in two stages just like the name suggests, it compresses air using one piston and uses the other to move compressed air from medium size tanks.

Finding the best air compressor

Whether you are purchasing a stationary air compressor or a portable air compressor, remember that it is always good to know the air requirements by calculating the air capacity and air volume so that you can determine the size. For larger tools such as pneumatic tools with large pipe diameters, consult your auto shop attendant as these types need a special size air compressor to ensure maximum flow of air. There are standard sizes too.

Air compressing safety

Consider the safety factor to the workers operating the air compressor before you even make the purchase. A very small air compressor, for example,  might put you at risk of damaging the machines especially if you are going to use it in an area that requires a large compressor. As far as safety is concerned, portable compressors require extra care to avoid dropping or banging them. 

In terms of durability, oil-lubricated compressors are more durable as compared to oil-free compressors. They are a bit more pricey though. They are also best suited for impact wrenches.

Energy efficiency

Electric air compressors are more energy efficient compared to belt-driven compressors. They are mainly used to run larger models of gasoline engines as they pump more gallons per minute on each square inch.  The air flow rate determines the air power and air output, which are key factors when it comes to performance

Lifespan

The quality of the air hoses determines the lifespan of air compressors. Always go for high quality air filters and hoses when shopping for air tools.

Conclusion

When shopping for a compressor, buy one with the inlet pressure in mind. This is because too much pressure will ruin a small power air compressor thus rendering it useless. Remember an air compressing size chart will save you a lot while shopping.  Regardless of the use, a size chart is a key part of ensuring you get to purchase a proper compressor for the job.

Remember there are several types of air compressors serving different purposes, so please be sure to select and buy according to your intended purpose. 

Did you find this guide helpful or would you like to ask some questions? Kindly like and leave a comment in the comments section and please feel free as well to share the tips with your friends.  

Picture in this post by Autoweek

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