Spray Gun CFM and Air Compressor Sizing Calculator
ANA›Life Services Authority›National Calculator Authority›Spray Gun CFM and Air Compressor Sizing Calculator
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Spray Gun CFM and Air Compressor Sizing Calculator
Calculate the total CFM (cubic feet per minute) required for your spray gun setup and determine the minimum air compressor size needed to run it continuously and efficiently.
Spray Gun CFM Requirement (CFM) ⓘThe CFM rating of your spray gun at its operating pressure. Check the manufacturer's spec sheet.
Number of Spray Guns Running Simultaneously ⓘHow many spray guns will be operating at the same time.
Spray Gun Duty Cycle (%) ⓘPercentage of time the spray gun is actively spraying. 100% means continuous use.
Additional Tools CFM (CFM) ⓘTotal CFM required by any other air tools running simultaneously (e.g. blow guns, sanders). Enter 0 if none.
Safety / Headroom Factor (%) ⓘRecommended 25–50% extra capacity above calculated demand to prevent compressor overheating and pressure drops.
Operating Pressure (PSI) ⓘThe pressure at which the spray gun operates. Typical HVLP guns: 25–30 PSI at the cap; conventional guns: 40–60 PSI.
Desired Tank Size (Gallons) — Optional ⓘEnter a tank size to see how long it can sustain spraying before the compressor must cycle on. Leave 0 to skip.
Calculate
function sprCalc() { var gunCfm = parseFloat(document.getElementById('spr-gun-cfm').value); var numGuns = parseFloat(document.getElementById('spr-num-guns').value); var dutyCycle = parseFloat(document.getElementById('spr-duty-cycle').value); var otherTools = parseFloat(document.getElementById('spr-other-tools').value); var safetyFactor = parseFloat(document.getElementById('spr-safety-factor').value); var psi = parseFloat(document.getElementById('spr-operating-psi').value); var tankGal = parseFloat(document.getElementById('spr-tank-size').value);
var errors = []; if (isNaN(gunCfm) || gunCfm 100) errors.push("Duty cycle must be between 1 and 100%."); if (isNaN(otherTools)|| otherTools 200) errors.push("Safety factor must be between 0 and 200%."); if (isNaN(psi) || psi 0) { document.getElementById('spr-result').innerHTML = 'Please fix the following:' + errors.map(function(e){ return ''; }).join('') + ''; return; }
// --- Core Calculations ---
// Effective CFM demand from spray guns accounting for duty cycle // Effective_Gun_CFM = Gun_CFM × Number_of_Guns × (Duty_Cycle / 100) var effectiveGunCfm = gunCfm * numGuns * (dutyCycle / 100);
// Total demand = effective gun CFM + other tools (other tools assumed 100% duty cycle) var totalDemandCfm = effectiveGunCfm + otherTools;
// Required compressor CFM with safety headroom // Required_CFM = Total_Demand_CFM × (1 + Safety_Factor / 100) var requiredCompressorCfm = totalDemandCfm * (1 + safetyFactor / 100);
// Compressor HP estimate: industry rule of thumb ~1 HP per 3–4 CFM at ~90 PSI // Adjusted for pressure: CFM_at_90 ≈ Required_CFM × (PSI / 90) // HP ≈ CFM_at_90_PSI / 3.5 (conservative mid-range factor) var cfmAt90 = requiredCompressorCfm * (psi / 90); var estimatedHp = cfmAt90 / 3.5;
// Tank runtime calculation (if tank size provided) // Usable air in tank (cubic feet) = Tank_Gallons / 7.48052 × (PSI / 14.696) // (converts gallons to cubic feet, then to free air at atmospheric pressure) // Runtime (minutes) = Usable_Air_CF / Required_CFM var tankRuntimeHtml = ''; if (tankGal > 0) { var tankCf = tankGal / 7.48052; var usableAirCf = tankCf * (psi / 14.696); var runtimeMin = usableAirCf / requiredCompressorCfm; var runtimeSec = runtimeMin * 60; tankRuntimeHtml = 'Tank Usable Air Volume' + usableAirCf.toFixed(2) + ' ft³' + 'Tank Runtime Before Compressor Cycles' + runtimeMin.toFixed(2) + ' min (' + runtimeSec.toFixed(0) + ' sec)'; }
// Compressor size recommendation var compressorRec = ""; if (requiredCompressorCfm ' + 'ParameterValue' + 'Effective Spray Gun CFM Demand' + effectiveGunCfm.toFixed(2) + ' CFM' + 'Total Air Demand (guns + other tools)' + totalDemandCfm.toFixed(2) + ' CFM' + 'Required Compressor CFM (with ' + safetyFactor + '% headroom)' + requiredCompressorCfm.toFixed(2) + ' CFM' + 'Estimated Compressor HP Needed' + estimatedHp.toFixed(1) + ' HP' + 'Operating Pressure' + psi + ' PSI' + tankRuntimeHtml + 'Recommended Compressor Class' + compressorRec + '' + ''; }
#### Formulas Used
1. Effective Gun CFM Demand: Effective_Gun_CFM = Gun_CFM × Number_of_Guns × (Duty_Cycle / 100)
2. Total Air Demand: Total_Demand_CFM = Effective_Gun_CFM + Other_Tools_CFM
3. Required Compressor CFM: Required_CFM = Total_Demand_CFM × (1 + Safety_Factor / 100)
4. Estimated Horsepower: CFM_at_90PSI = Required_CFM × (Operating_PSI / 90) HP ≈ CFM_at_90PSI / 3.5 (Industry rule of thumb: ~3.5 CFM per HP at 90 PSI for single-stage compressors)
5. Tank Runtime (if tank size entered): Tank_Volume_ft³ = Tank_Gallons / 7.48052 Usable_Air_ft³ = Tank_Volume_ft³ × (PSI / 14.696) Runtime_min = Usable_Air_ft³ / Required_CFM
#### Assumptions & References
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