The calculation starts with overlap

List the air tools that may operate at the same time. Then copy each exact model's published airflow field, unit and pressure. Add a group only when those details line up.

The basic arithmetic is:

simultaneous published demand = tool A rating + tool B rating + ...

The difficult part is deciding which published ratings belong in the same sum. Average Air Consumption is not the same field as Air Consumption @ Load. CFM is not automatically interchangeable with SCFM. A figure at 40 PSI does not belong in a 90 PSI total.

A four-step method

  1. Identify simultaneous tools. Use the actual overlap in the job, not every tool you own.
  2. Copy the whole specification. Keep the model, field label, unit and pressure beside the number.
  3. Group compatible fields. Add average with average or under-load with under-load at the same stated pressure and unit.
  4. Add the omitted system checks. Hose loss, leaks, compressor duty cycle, recovery and control behaviour remain outside the simple total.

This creates an auditable starting point without turning catalogue arithmetic into a performance guarantee.

Worked example: two published average fields

Suppose two people use these sanders simultaneously:

Tool Exact manufacturer field Published figure
Astro 325 finishing palm sander Average Air Consumption 5.5 CFM at 90 PSI
Astro 3035 belt sander Average Air Consumption 4 CFM at 90 PSI
Sum of published average fields 9.5 CFM at 90 PSI

The Campbell Hausfeld VT6271 publishes 10.2 CFM at 90 PSI. Its published output is therefore 0.7 CFM above the 9.5 CFM sum.

That 0.7 CFM difference does not prove the compressor will sustain both sanders. The Astro pages label their figures as average consumption but do not define them as full-trigger demand or state one shared duty-cycle formula. The comparison is useful because it exposes the narrow numerical margin and the evidence still missing.

When the multiply-by-four estimate applies

Quincy Compressor describes a rule for a specific situation: if a tool's stated CFM is based on a 25 percent duty cycle and the tool will instead operate continuously, the planner may need to multiply that figure by four.

Applied conditionally to the two-sander sum:

9.5 CFM × 4 = 38 CFM at 90 PSI

This is a Quincy-style planning estimate only if both input ratings genuinely represent 25 percent duty-cycle use. The Astro product pages used above do not establish that premise, so 38 CFM must not be presented as the tools' verified continuous requirement. Ask the tool maker for a load or continuous-use figure when sustained operation controls the purchase.

A three-tool average-field example

The same method works for a larger station:

Tool Exact manufacturer field Published figure
Astro 1128 mini impact ratchet Average Air Consumption 3.1 CFM at 90 PSI
Universal Tool UT8706-2 pencil grinder Average Air Consumption 4 CFM at 90 PSI
Universal Tool UT8891-5 angle drill Average Air Consumption 4 CFM at 90 PSI
Sum of published average fields 11.1 CFM at 90 PSI

The sum is exact arithmetic on three average fields. It is not proof of 11.1 CFM full-trigger demand. If the station's work pattern involves long overlapping runs, the next step is obtaining the appropriate operating field from each manufacturer.

A clean under-load example

Ingersoll Rand publishes under-load figures for both of these tools:

Tool Exact manufacturer field Published figure
Ingersoll Rand 293 impact wrench Air Consumption @ Load 64 CFM at 90 PSI
Ingersoll Rand 99HL60H106 Type 1 grinder Air Consumption @ Load 84 CFM at 90 PSI
Combined under-load fields 148 CFM at 90 PSI

Here, the labels, units and pressure match. The 148 CFM total is therefore a coherent sum of two manufacturer-published under-load fields. It still excludes pressure loss and compressor operating limits, but it does not mix average and load conditions.

Tool duty cycle and compressor duty cycle are different

Tool usage duty cycle describes how often a tool consumes air during the job. Compressor duty cycle limits how long the compressor itself may run within a stated period or operating condition.

A calculated airflow total does not override the compressor's duty-cycle, ventilation or temperature limits. A compressor can publish an airflow figure at 90 PSI and still be unsuitable for the planned run time. Check the compressor manual separately.

What the sum leaves out

The addition does not account for:

  • pressure drop through hose, pipe, fittings, filters and regulators;
  • leaks in the distribution system;
  • the compressor's permitted duty cycle and recovery behaviour;
  • simultaneous demand elsewhere on the same air system;
  • control strategy in a multi-compressor installation.

Read how hose length and inside diameter affect pressure at the tool before treating a tank-side rating as tool-end pressure. For permanent distribution or electrical changes, follow the equipment manuals and use qualified installers.

Put the total to work

The matcher compares one tool field with one compressor record at the same stated pressure. It does not add a workshop list automatically. Use this page to build the list, then inspect individual records and source labels in the matcher.

The guide to comparing CFM at the same PSI explains why pressure must remain attached to every number.

Sources checked

Manufacturer pages can change. Recheck every exact model and operating condition before designing a shared air supply.