Convert between ACFM (Actual Cubic Feet per Minute) and SCFM (Standard Cubic Feet per Minute).
ACFM to SCFM (Actual to Standard)
SCFM to ACFM (Standard to Actual)
Enter the gauge pressure (system pressure read from a dial).
Enter the actual temperature of the gas at the measuring point.
Calculated Flow Rate
Based on Standard Conditions of 14.7 PSIA and 68°F:
0
Understanding Gas Flow Rate Conversion
In pneumatic systems, compressor sizing, and process engineering, accurately measuring gas flow is critical. However, gas volume changes significantly with pressure and temperature. This Gas Flow Rate Conversion Calculator helps engineers and technicians convert between actual working conditions (ACFM) and a standardized baseline (SCFM).
Note on Standard Conditions: This calculator uses the common industrial standard for compressed air:
14.7 PSIA (Sea Level Atmospheric Pressure) and 68°F (528° Rankine).
ACFM vs. SCFM: What is the Difference?
ACFM (Actual Cubic Feet per Minute): This is the volume of gas flowing anywhere in a system under the actual conditions of pressure and temperature at that specific point. It is useful for sizing actual equipment like fans or measuring volumetric displacement.
SCFM (Standard Cubic Feet per Minute): This is the flow rate referenced back to "standard" conditions (usually sea level pressure and 68°F). SCFM represents the actual mass or number of molecules of gas. It allows for comparison between different systems regardless of their operating environment.
The Conversion Formulas
To convert between these two metrics, we use the Ideal Gas Law. The logic assumes that the mass of the air remains constant while the volume changes based on pressure and temperature ratios.
Calculating SCFM from ACFM
To find the Standard Flow when you know the Actual Flow, Pressure, and Temperature:
SCFM = ACFM × (Pact / Pstd) × (Tstd / Tact)
Calculating ACFM from SCFM
To find the Actual Flow at a specific operating point when you know the Standard Flow:
ACFM = SCFM × (Pstd / Pact) × (Tact / Tstd)
Key Definitions for Calculation
Pact (Actual Pressure): Must be in Absolute Pressure (PSIA). Formula: Gauge Pressure (PSIG) + 14.7
Tact (Actual Temperature): Must be in Absolute Temperature (Rankine). Formula: Fahrenheit + 459.67
Pstd: 14.7 PSIA
Tstd: 528° Rankine (68°F)
Practical Example
Imagine a compressor is delivering 100 CFM (measured at the outlet) at a gauge pressure of 100 PSIG and a temperature of 100°F.
To find out how much "standard" air this represents (SCFM):
Convert Pressure: 100 PSIG + 14.7 = 114.7 PSIA.
Convert Temperature: 100°F + 460 = 560°R.
Apply Ratio: 100 × (114.7 / 14.7) × (528 / 560).
Result: Approx 735 SCFM.
The air is compressed to roughly 1/7th of its original volume, so 100 cubic feet of compressed air actually contains about 735 cubic feet of air at atmospheric pressure.
function updateLabels() {
var type = document.getElementById('conversionType').value;
var label = document.getElementById('flowLabel');
if (type === 'ACFMtoSCFM') {
label.innerText = 'Input Flow Rate (ACFM)';
} else {
label.innerText = 'Input Flow Rate (SCFM)';
}
}
function calculateGasFlow() {
// Inputs
var type = document.getElementById('conversionType').value;
var flowInput = document.getElementById('flowRate').value;
var pressureInput = document.getElementById('pressure').value;
var tempInput = document.getElementById('temperature').value;
// Validation
if (flowInput === " || pressureInput === " || tempInput === ") {
alert('Please fill in all fields (Flow Rate, Pressure, and Temperature).');
return;
}
var flow = parseFloat(flowInput);
var pressureGauge = parseFloat(pressureInput);
var tempF = parseFloat(tempInput);
if (isNaN(flow) || isNaN(pressureGauge) || isNaN(tempF)) {
alert('Please enter valid numbers.');
return;
}
if (flow < 0) {
alert('Flow rate cannot be negative.');
return;
}
// Standard Conditions (CAGI / Common Industrial)
// Standard Pressure = 14.7 PSIA
// Standard Temp = 68 F = 527.67 R (Rounded to 528 for general engineering)
var pStd = 14.7;
var tStdR = 527.67;
// Convert Actual Inputs to Absolute
var pActAbs = pressureGauge + 14.7; // PSIG to PSIA
var tActR = tempF + 459.67; // F to Rankine
var result = 0;
var resultUnit = '';
var formulaText = '';
if (type === 'ACFMtoSCFM') {
// Formula: SCFM = ACFM * (P_act / P_std) * (T_std / T_act)
result = flow * (pActAbs / pStd) * (tStdR / tActR);
resultUnit = ' SCFM';
document.getElementById('resultTitle').innerText = 'Converted Flow Rate (SCFM)';
formulaText = 'Correction Factor: P_ratio (' + (pActAbs/pStd).toFixed(2) + ') * T_ratio (' + (tStdR/tActR).toFixed(2) + ')';
} else {
// Formula: ACFM = SCFM * (P_std / P_act) * (T_act / T_std)
result = flow * (pStd / pActAbs) * (tActR / tStdR);
resultUnit = ' ACFM';
document.getElementById('resultTitle').innerText = 'Converted Flow Rate (ACFM)';
formulaText = 'Correction Factor: P_ratio (' + (pStd/pActAbs).toFixed(2) + ') * T_ratio (' + (tActR/tStdR).toFixed(2) + ')';
}
// Display Results
var resultBox = document.getElementById('resultBox');
var resultDiv = document.getElementById('finalResult');
var ratioDiv = document.getElementById('ratioInfo');
resultBox.style.display = 'block';
resultDiv.innerHTML = result.toFixed(2) + resultUnit;
ratioDiv.innerHTML = formulaText;
}