Air Flow Rate Conversion Calculator

Air Flow Rate Converter

function calculateAirFlow() { var valInput = document.getElementById('flowValue').value; var fromUnit = document.getElementById('fromUnit').value; var toUnit = document.getElementById('toUnit').value; var resultBox = document.getElementById('resultBox'); var resultValue = document.getElementById('resultValue'); var resultUnitDisplay = document.getElementById('resultUnit'); var formulaDisplay = document.getElementById('formulaDisplay'); if (valInput === "" || isNaN(valInput)) { alert("Please enter a valid numeric flow rate."); return; } var value = parseFloat(valInput); // Base unit is CFM (Cubic Feet per Minute) // Factors define: 1 Unit = X CFM var factorsToCFM = { 'cfm': 1.0, 'm3h': 0.588577779, 'ls': 2.118880003, 'm3s': 2118.880003, 'm3min': 35.3146667 }; var unitLabels = { 'cfm': 'CFM', 'm3h': 'm³/h', 'ls': 'L/s', 'm3s': 'm³/s', 'm3min': 'm³/min' }; // Convert Input to CFM (Base) var valInCFM = value * factorsToCFM[fromUnit]; // Convert CFM to Output var finalResult = valInCFM / factorsToCFM[toUnit]; // Formatting var displayResult = finalResult < 0.001 && finalResult !== 0 ? finalResult.toExponential(4) : finalResult.toLocaleString('en-US', {maximumFractionDigits: 4}); resultValue.innerHTML = displayResult; resultUnitDisplay.innerHTML = unitLabels[toUnit]; // Formula explanation logic var factor = factorsToCFM[fromUnit] / factorsToCFM[toUnit]; var formulaText = "Formula: " + value + " " + unitLabels[fromUnit] + " × " + factor.toFixed(5) + " = " + displayResult + " " + unitLabels[toUnit]; formulaDisplay.innerHTML = formulaText; resultBox.style.display = 'block'; }

Understanding Air Flow Rate Conversions

In the fields of HVAC (Heating, Ventilation, and Air Conditioning), industrial engineering, and fluid dynamics, accurately converting air flow rates is critical for system sizing and performance analysis. Whether you are working with American standards like CFM (Cubic Feet per Minute) or metric standards like m³/h (Cubic Meters per Hour), using the correct conversion factors ensures your fans, ducts, and filters operate efficiently.

Common Air Flow Units

• CFM (Cubic Feet per Minute): The standard measurement in the United States and Imperial systems. It measures the volume of air in cubic feet that passes a stationary point in one minute.
• m³/h (Cubic Meters per Hour): The most common metric unit for ventilation volume, widely used in Europe and Asia.
• L/s (Liters per Second): Often used in precision engineering and smaller ventilation systems.
• m³/s (Cubic Meters per Second): The SI unit for volumetric flow rate, typically reserved for large-scale industrial calculations.

Air Flow Conversion Table

Use the following table to manually calculate conversions between the most common air flow units. The factors below represent the multiplier required to convert 1 unit of the left column into the top row unit.

From / To	CFM	m³/h	L/s
1 CFM	1	1.699	0.4719
1 m³/h	0.5886	1	0.2778
1 L/s	2.119	3.6	1

Why is Conversion Important?

HVAC Sizing: An air conditioner specified in BTU often requires a specific airflow in CFM to function correctly (typically 400 CFM per ton of cooling). If a fan is rated in m³/h, failing to convert correctly could lead to a system that freezes up (too little air) or fails to dehumidify (too much air).

Example Calculation

Let's say you have a European exhaust fan rated at 500 m³/h and you need to know if it meets a requirement of 300 CFM.

Using the conversion factor: $$1 \text{ m}^3/\text{h} \approx 0.5886 \text{ CFM}$$

Calculation:

$$500 \times 0.5886 = 294.3 \text{ CFM}$$

In this scenario, the fan provides 294.3 CFM, which is slightly below the 300 CFM requirement.

Frequently Asked Questions

What is the difference between Actual CFM (ACFM) and Standard CFM (SCFM)?

The calculator above assumes standard conditions. ACFM is the actual volume of air flowing, while SCFM corrects that volume to standard temperature and pressure conditions (usually sea level and 68°F). In pressurized systems or high altitudes, you must apply density corrections to convert between ACFM and SCFM.

How do I convert CFM to m³/min?

To convert Cubic Feet per Minute to Cubic Meters per Minute, multiply the CFM value by approximately 0.02832.