kg/s (Kilograms per second)
kg/h (Kilograms per hour)
kg/min (Kilograms per minute)
lb/s (Pounds per second)
lb/min (Pounds per minute)
lb/h (Pounds per hour)
t/h (Metric Tonnes per hour)
kg/m³ (Kilograms per cubic meter)
g/cm³ (Grams per cubic centimeter)
lb/ft³ (Pounds per cubic foot)
lb/gal (Pounds per US Gallon)
Density must be greater than zero.
m³/s (Cubic meters per second)
m³/h (Cubic meters per hour)
L/s (Liters per second)
L/min (Liters per minute)
GPM (US Gallons per minute)
ft³/s (Cubic feet per second)
CFM (Cubic feet per minute)
Volume Flow Rate (V̇)
0.00
function calculateVolumeFlow() {
// 1. Get Input Values
var massVal = document.getElementById('massFlowInput').value;
var massUnit = document.getElementById('massUnit').value;
var densityVal = document.getElementById('densityInput').value;
var densityUnit = document.getElementById('densityUnit').value;
var outUnit = document.getElementById('outputUnitSelect').value;
var errorDiv = document.getElementById('densityError');
var resultBox = document.getElementById('resultBox');
// 2. Validate
if (massVal === "" || densityVal === "") {
alert("Please enter both Mass Flow Rate and Density values.");
return;
}
var m = parseFloat(massVal);
var d = parseFloat(densityVal);
if (d <= 0) {
errorDiv.style.display = 'block';
resultBox.style.display = 'none';
return;
}
errorDiv.style.display = 'none';
// 3. Convert Mass Flow to SI base unit (kg/s)
var m_kgs = 0;
switch(massUnit) {
case 'kg_s': m_kgs = m; break;
case 'kg_min': m_kgs = m / 60; break;
case 'kg_h': m_kgs = m / 3600; break;
case 'lb_s': m_kgs = m * 0.45359237; break;
case 'lb_min': m_kgs = (m * 0.45359237) / 60; break;
case 'lb_h': m_kgs = (m * 0.45359237) / 3600; break;
case 't_h': m_kgs = (m * 1000) / 3600; break;
}
// 4. Convert Density to SI base unit (kg/m³)
var d_kgm3 = 0;
switch(densityUnit) {
case 'kg_m3': d_kgm3 = d; break;
case 'g_cm3': d_kgm3 = d * 1000; break;
case 'lb_ft3': d_kgm3 = d * 16.018463; break;
case 'lb_gal': d_kgm3 = d * 119.826427; break;
}
// 5. Calculate Volume Flow in SI base (m³/s)
// Formula: V = m / rho
var v_m3s = m_kgs / d_kgm3;
// 6. Convert Result to Target Output Unit
var finalVal = 0;
var unitLabel = "";
switch(outUnit) {
case 'm3_s':
finalVal = v_m3s;
unitLabel = "m³/s";
break;
case 'm3_h':
finalVal = v_m3s * 3600;
unitLabel = "m³/h";
break;
case 'l_s':
finalVal = v_m3s * 1000;
unitLabel = "L/s";
break;
case 'l_min':
finalVal = v_m3s * 60000;
unitLabel = "L/min";
break;
case 'gal_min':
finalVal = v_m3s * 15850.3231; // US GPM
unitLabel = "GPM";
break;
case 'ft3_s':
finalVal = v_m3s * 35.3146667;
unitLabel = "ft³/s";
break;
case 'ft3_min':
finalVal = v_m3s * 2118.88; // CFM
unitLabel = "CFM";
break;
}
// 7. Display Results
resultBox.style.display = 'block';
// Formatting numbers to nice precision
var displayVal = finalVal 0 ? finalVal.toExponential(4) : finalVal.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 4});
document.getElementById('finalResult').innerHTML = displayVal + " " + unitLabel + "";
// Show steps
var stepsHtml = "Calculation Steps:";
stepsHtml += "1. Mass Flow converted to SI: " + m_kgs.toPrecision(4) + " kg/s";
stepsHtml += "2. Density converted to SI: " + d_kgm3.toPrecision(4) + " kg/m³";
stepsHtml += "3. Formula (V̇ = ṁ / ρ): " + m_kgs.toPrecision(4) + " / " + d_kgm3.toPrecision(4) + " = " + v_m3s.toPrecision(4) + " m³/s";
document.getElementById('conversionSteps').innerHTML = stepsHtml;
}
Understanding Mass Flow to Volume Flow Conversion
In fluid dynamics, engineering, and chemical processing, converting between mass flow rate and volume flow rate is a fundamental calculation. While mass flow rate measures the amount of mass passing through a point over time (e.g., kilograms per second), volume flow rate measures the volume of fluid passing through that point (e.g., liters per minute).
The bridge between these two metrics is Density. Because the volume of a fluid can change with temperature and pressure (especially for gases), knowing the specific density of the substance at operating conditions is critical for accurate conversion.
V̇ = ṁ / ρ
Where:
V̇ (V-dot) = Volume Flow Rate (e.g., m³/s)
ṁ (m-dot) = Mass Flow Rate (e.g., kg/s)
ρ (rho) = Density of the fluid (e.g., kg/m³)
Why is this conversion important?
Different industries rely on different metrics. For example:
Chemical Reactions: Stoichiometry depends on the mass of reactants, so mass flow controllers are often used.
Pumps and Fans: These devices are typically sized based on volume flow rate (GPM or CFM).
Fuel Systems: Aviation fuel is often measured in mass (pounds or kg) because energy content correlates with mass, but the fuel pumps operate on volume.
How to Use This Calculator
Enter the Mass Flow Rate: Input the value and select the unit (e.g., 500 kg/h).
Enter the Density: Input the density of the fluid. Common values include 1000 kg/m³ for water or roughly 1.225 kg/m³ for air at sea level.
Select Output Unit: Choose the unit you wish to see the result in, such as Gallons Per Minute (GPM) or Cubic Meters per Hour (m³/h).
Calculate: Click the button to see the converted volume flow rate.
Common Density Reference Table
Here are approximate density values for common fluids to help with your calculations:
Fluid
Density (kg/m³)
Density (lb/ft³)
Water (4°C)
1000
62.4
Seawater
1025
64.0
Gasoline
700 – 750
43.7 – 46.8
Diesel Fuel
830 – 850
51.8 – 53.0
Air (20°C, 1 atm)
1.204
0.075
Example Calculation
Suppose you have a pump moving water at a rate of 10,000 kg/h. You need to know the flow rate in Liters per minute (L/min).
1. Convert mass flow to kg/s: 10,000 / 3600 = 2.778 kg/s.
2. Identify Density of water: ~1000 kg/m³.
3. Calculate Volume Flow (SI): 2.778 / 1000 = 0.002778 m³/s.
4. Convert to L/min: 0.002778 m³/s * 60,000 (conversion factor) = 166.68 L/min.