HVAC Refrigerant Charging Card
One page. Superheat, subcooling and PT for four refrigerants.
$3.99
BuyCFM Calculator
Air compressor sizing for single tools, mixed tool sets, and quick estimates
Calculate required CFM, recommended compressor output, minimum PSI, and tank-size guidance based on your real usage pattern.
HVAC
Complete HVAC Charging Guide
15 pages. Full superheat grid, PT tables, A2L safety and diagnosis.
$12.99
Buy
HVAC Job Estimator
Quote HVAC work and catch a refrigerant mismatch before you order.
Excel or Google Sheets. Best on a computer.
$29.00
BuyBEST VALUE
HVAC Complete Bundle
Card, 15-page guide and the estimator workbook. All six files.
Excel or Google Sheets. Best on a computer.
$34.99
$45.98 if bought separately — save $10.99
BuyCheckout opens here — you stay on this page.
Recommended Air Compressors and Accessories
Sized to match the CFM ranges from this calculator.
Porter Cable 6-Gallon Pancake
- 2.6 CFM @ 90 PSI for lighter pneumatic tasks
- Compact footprint for home and mobile use
- Good starting option for occasional shop work
Craftsman 20-Gallon Vertical
- 5.0 CFM @ 90 PSI for medium demand
- Larger receiver buffer for reduced cycling
- Practical home garage compressor class
Ingersoll-Rand 5.5HP Gas
- Higher output for demanding air workflows
- Works where line power is unavailable
- Built for heavier duty-cycle applications
Relhost 65ft Retractable Reel
- Reduces hose clutter and trip hazards
- Extends usable compressor reach in shop bays
- Better hose management for daily work
Air Pressure Regulator and Gauge
- Dial pressure to match tool requirements
- Moisture trap protects pneumatic equipment
- Improves consistency for paint and precision work
As an Amazon Associate, TestTalkHQ earns from qualifying purchases. Prices and availability may change.
Diagnose Problems & Choose Tank vs CFM
When the numbers look right but shop air still fails, use Air Compressor Troubleshooting for leaks, short-cycling, short runtime, pressure drop under load, and moisture. When you are deciding whether to buy gallons or delivery, read Bigger Tank vs More CFM.
How to Use the CFM Calculator
Select single-tool, multi-tool, or quick estimate mode. Enter realistic duty cycle and operating profile, then calculate required and recommended CFM with baseline tank guidance.
CFM vs PSI
CFM is airflow volume; PSI is air pressure. You need adequate flow and enough pressure for your highest-demand tool to avoid power drop during use.
Duty cycle impact
The calculator scales tool CFM by duty cycle to estimate average load. Continuous operations require significantly more compressor headroom than intermittent workflows.
Frequently Asked Questions
Why add 25-50% CFM margin?
Margin improves compressor longevity, reduces heat, and helps maintain pressure stability under dynamic shop loads.
Can one compressor run every tool at once?
Usually no. Multi-tool mode applies a diversity factor because not all tools run at full duty simultaneously.
When should I move to a two-stage compressor?
High continuous demand and large airflow requirements generally favor two-stage compressors for better efficiency and sustained output.
What this calculator does
Size an air compressor for one tool, a mixed shop, or a quick estimate by shop type. It converts tool CFM and duty cycle into required flow, adds a recommended CFM buffer, and suggests minimum PSI and tank size so the compressor does not sag under real use. Built for plasma cutters, spray guns, grinders, impacts, and other pneumatic gear common in fab and automotive bays.
What each input means
- Mode (single, multiple, quick): Single tool for one machine; multiple for a checklist of everything you run; quick for shop-type presets.
- Tool type: Preset CFM and PSI for common tools (plasma, HVLP, sanders, impacts, etc.).
- Duty cycle: Percent of time the tool actually flows air—100% continuous vs 25% intermittent changes required CFM sharply.
- Custom CFM and PSI: When your tool is not listed, enter nameplate or manual values.
- Multiple-tool selections: Each tool’s duty cycle in a mixed shop; simultaneous use is assumed from your selections.
- Shop type and simultaneous tools (quick mode): Hobby, automotive, fabrication, or paint-focused defaults with how many tools run at once.
Using the results on the job
Buy compressor rated at or above recommended CFM at 90 PSI (or your highest tool PSI), not peak marketing numbers at 40 PSI. Undersized units cause plasma arc drop, inconsistent spray, and short tool life. Oversize tank before you oversize HP when bursts are short but heavy—tank stores air between cycles. Plumb regulators at each drop so paint and plasma see stable pressure, and note that long undersized hose runs steal effective CFM at the tool.
Multiple-tool mode is only as good as the duty cycles you enter—be honest if two grinders run together during fab rush. Quick estimate mode is for budgeting a first machine; rerun in single-tool mode before you buy plasma or a large sander. Dry the air for paint and plasma; moisture shows up as bad cuts and fish eyes before it shows on the CFM math.