Volumetric Flow Rate to Mass Flow Rate Calculator

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Volumetric to Mass Flow Calculator

Convert volume flow (e.g., m³/s, CFM) to mass flow (e.g., kg/s, lb/hr) instantly.

m³/s m³/h L/min ft³/s CFM (ft³/min) GPM (US)
kg/m³ g/cm³ lb/ft³ lb/gal
Quick Presets:
Water (1000 kg/m³)
Air (1.225 kg/m³)
Crude Oil (870 kg/m³)
Mercury (13560 kg/m³)
kg/s (Kilograms per second) kg/h (Kilograms per hour) lb/s (Pounds per second) lb/h (Pounds per hour) t/h (Metric Tonnes per hour)
Calculated Mass Flow Rate:
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Understanding Volumetric Flow to Mass Flow Conversion

In fluid dynamics and engineering, converting between volumetric flow rate and mass flow rate is a fundamental calculation. This calculator helps engineers, technicians, and students quickly convert volume-based measurements (like liters per minute or CFM) into mass-based measurements (like kilograms per second or pounds per hour) by incorporating the fluid's density.

Mass Flow Rate (ṁ) = Volumetric Flow Rate (Q) × Density (ρ)

Where:

  • ṁ (m-dot): Mass Flow Rate (mass per unit time)
  • Q: Volumetric Flow Rate (volume per unit time)
  • ρ (rho): Density of the fluid (mass per unit volume)

Why is this conversion important?

Volumetric flow rate depends on temperature and pressure because fluids (especially gases) expand and contract. Mass flow rate, however, remains constant regardless of pressure or temperature changes (assuming no mass is added or lost). For applications involving combustion, chemical reactions, or precise billing (like natural gas custody transfer), knowing the actual mass of the substance flowing is far more critical than the volume.

Common Density Values

The accuracy of your calculation depends heavily on the density value used. Here are standard densities for common fluids at standard conditions (approx. 20°C / 68°F and 1 atm):

Fluid Density (kg/m³) Density (lb/ft³)
Fresh Water 998 62.3
Sea Water 1,025 64.0
Air 1.204 0.075
Gasoline 720 45.0
Diesel Fuel 832 51.9
Propane (Liquid) 493 30.8

Example Calculation

Scenario: Water is flowing through a pipe at a rate of 500 Liters per minute. You need to calculate the mass flow rate in kg/s.

  1. Identify Q: 500 L/min.
  2. Identify Density (ρ): Water is approximately 1000 kg/m³.
  3. Convert Q to base units (m³/s):
    500 L/min ÷ 60,000 = 0.00833 m³/s.
  4. Apply Formula:
    ṁ = 0.00833 m³/s × 1000 kg/m³ = 8.33 kg/s.
function setFluid(type) { var densityInput = document.getElementById('density'); var densityUnit = document.getElementById('densityUnit'); // Reset unit to kg/m3 for presets for simplicity, user can change after densityUnit.value = 'kg_m3'; if (type === 'water') { densityInput.value = 1000; } else if (type === 'air') { densityInput.value = 1.225; } else if (type === 'oil') { densityInput.value = 870; } else if (type === 'mercury') { densityInput.value = 13560; } } function calculateMassFlow() { // 1. Get Inputs var qVal = parseFloat(document.getElementById('volFlow').value); var qUnit = document.getElementById('volUnit').value; var rhoVal = parseFloat(document.getElementById('density').value); var rhoUnit = document.getElementById('densityUnit').value; var outUnit = document.getElementById('massUnit').value; // Validation if (isNaN(qVal) || isNaN(rhoVal)) { alert("Please enter valid numerical values for Flow Rate and Density."); return; } if (qVal < 0 || rhoVal < 0) { alert("Values cannot be negative."); return; } // 2. Convert Vol Flow to base unit (m3/s) var qBase = 0; // in m3/s switch(qUnit) { case 'm3_s': qBase = qVal; break; case 'm3_h': qBase = qVal / 3600; break; case 'l_min': qBase = qVal / 60000; break; case 'ft3_s': qBase = qVal * 0.0283168; break; case 'cfm': // ft3/min qBase = qVal * 0.000471947; break; case 'gpm_us': qBase = qVal * 0.0000630902; break; } // 3. Convert Density to base unit (kg/m3) var rhoBase = 0; // in kg/m3 switch(rhoUnit) { case 'kg_m3': rhoBase = rhoVal; break; case 'g_cm3': rhoBase = rhoVal * 1000; break; case 'lb_ft3': rhoBase = rhoVal * 16.0185; break; case 'lb_gal': rhoBase = rhoVal * 119.826; break; } // 4. Calculate Mass Flow in base unit (kg/s) var massBase = qBase * rhoBase; // kg/s // 5. Convert to Desired Output Unit var finalResult = 0; var unitLabel = ""; switch(outUnit) { case 'kg_s': finalResult = massBase; unitLabel = "kg/s"; break; case 'kg_h': finalResult = massBase * 3600; unitLabel = "kg/h"; break; case 'lb_s': finalResult = massBase * 2.20462; unitLabel = "lb/s"; break; case 'lb_h': finalResult = massBase * 7936.64; unitLabel = "lb/h"; break; case 't_h': // Metric tonnes per hour finalResult = (massBase * 3600) / 1000; unitLabel = "t/h"; break; } // 6. Display Result var displayEl = document.getElementById('result-container'); var valueEl = document.getElementById('massFlowResult'); var stepsEl = document.getElementById('calculation-steps'); displayEl.style.display = 'block'; valueEl.innerHTML = finalResult.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 4}) + " " + unitLabel; // Show logic summary stepsEl.innerHTML = "Calculation Logic:" + "1. Converted Flow to SI: " + qBase.toExponential(3) + " m³/s" + "2. Converted Density to SI: " + rhoBase.toFixed(2) + " kg/m³" + "3. Base Mass Flow (m³⁄s × kg⁄m³): " + massBase.toFixed(4) + " kg/s" + "4. Converted to output unit: " + finalResult.toFixed(4) + " " + unitLabel; }

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