Dial in airflow before spraying fertilizers or sealants. See CFM, pressure, and reserve margins instantly. Download a report and match your compressor confidently now.
| Scenario | Working psi | Rated CFM @ psi | Hose | Guns | Recommended SCFM |
|---|---|---|---|---|---|
| Small garden sprayer finish coat | 20 | 6 @ 18 | 10 m, 8 mm | 1 | ~8–10 |
| Fence sealer with high volume gun | 25 | 12 @ 29 | 15 m, 8 mm | 1 | ~16–20 |
| Two operators on large bed edging | 25 | 10 @ 23 | 10 m, 10 mm | 2 | ~28–35 |
1) Pressure scaling:
Air demand is scaled between rated and working pressures using an orifice-flow approximation:
SCFM_work ≈ SCFM_rated × √(Pabs_work / Pabs_rated),
where Pabs = psi + 14.7.
2) Nozzle influence:
A gentle factor is applied for nozzle size:
NozzleFactor ≈ (Nozzle_mm / 1.4)^0.35.
This keeps the estimate stable while reflecting typical trends.
3) Hose and fitting losses: Pressure drop is estimated from flow, hose length, hose ID, and couplers. Supply pressure is increased to keep the working pressure at the gun.
4) Compressor recommendation:
Recommended ≈ TotalDemand × (1 + Reserve) ÷ Efficiency.
Duty cycle is also shown as an average demand indicator.
Consistent atomization depends on stable air delivery. This calculator estimates total demand in standard cubic feet per minute (SCFM), then adds reserve and efficiency allowances for realistic compressor sizing. Use it when applying fence sealers, deck coatings, raised-bed finishes, or plant-safe protective films where an even pattern matters.
Many spray tools list airflow at a specific pressure, but your working pressure may differ. The calculator scales demand using absolute pressure (psi plus atmospheric pressure) to approximate how flow changes with regulator settings. This helps prevent under-sizing when you increase pressure to improve fan width, or reduce it for softer application on delicate surfaces.
Long hoses and restrictive couplers can quietly steal pressure at the gun. The built-in loss estimator converts your hose length, inside diameter, and fitting count into a pressure-drop value, then raises the required supply pressure to compensate. A larger hose ID typically improves stability, especially when moving around beds, planters, or long fence lines.
If two operators spray at once, demand adds almost linearly. The calculator multiplies adjusted SCFM by the number of guns, and also shows average consumption using duty cycle. Duty cycle is useful for planning runtime and refill intervals, while the compressor recommendation targets peak delivery so pressure does not sag during long trigger pulls.
Delivered airflow is the key number, not motor horsepower. The recommendation applies reserve margin and an efficiency factor, producing a practical target SCFM. Tank guidance is given as a smoothing range to reduce pulsing, improve pattern repeatability, and limit moisture carryover. Re-check results after changing nozzles, coatings, or hose routing.
CFM is actual volumetric flow at conditions in the line. SCFM is corrected to standard conditions, making comparisons consistent. This calculator reports SCFM so you can match tool demand with compressor delivery ratings more reliably.
Smaller hoses create higher pressure loss at the same flow. To keep working pressure at the gun, the compressor must supply higher upstream pressure, which increases required airflow. Using a larger inside diameter often reduces this penalty.
Use manufacturer ratings when available because they reflect your exact tool. Presets are helpful for early planning or when labels are missing. If results feel high or low, verify the gun’s spec plate and regulator reading at the handle.
For short bursts, 10–15% reserve can be enough. For long passes, thicker coatings, or variable hose routing, 20–30% improves stability. If you see pulsing or fan shrink, increase reserve or reduce restrictions.
Air density drops with altitude, so you need more volumetric airflow to achieve similar mass flow and performance. The calculator applies a density-based correction, which can raise recommended delivery at higher elevations.
Use tank guidance as a smoothing aid, not a guarantee. Compressor delivery still matters most. Tanks help reduce cycling and pulsing, but an undersized compressor will eventually fall behind during continuous spraying.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.