Calculator Inputs
Use the method selector to switch between common engineering approaches for mass flow calculations.
Example Data Table
| Scenario | Method | Key Inputs | Mass Flow Rate |
|---|---|---|---|
| Cooling water branch | Density × Velocity × Area | 998 kg/m³, 2.4 m/s, 0.015 m² | 35.928 kg/s |
| Light oil transfer | Density × Volumetric Flow | 860 kg/m³, 1.8 m³/h | 0.430 kg/s |
| Ventilation line | Pipe Diameter × Velocity | 1.225 kg/m³, 3.1 m/s, 80 mm | 0.0191 kg/s |
| Compressed air nozzle | Ideal Gas Density Method | 300 kPa, 35°C, 28.97 g/mol, 18 m/s, 0.0025 m² | 0.1526 kg/s |
Formula Used
Direct area method: ṁ = ρ × v × A
Volumetric method: ṁ = ρ × Q
Pipe method: A = πD²/4, then ṁ = ρ × v × A
Ideal gas method: ρ = (P × M) / (R × T), then ṁ = ρ × v × A
Reynolds number: Re = (ρ × v × D) / μ
Here, ṁ is mass flow rate, ρ is density, v is average velocity, A is cross-sectional area, Q is volumetric flow, D is hydraulic or pipe diameter, μ is dynamic viscosity, P is absolute pressure, M is molecular weight, R is the universal gas constant, and T is absolute temperature.
How to Use This Calculator
- Select the engineering method that matches your available data.
- Enter the known values and choose the correct units.
- Add optional viscosity and diameter when Reynolds number matters.
- Click the calculate button to display results above the form.
- Review the converted outputs in kg/s, kg/h, lb/s, lb/h, and t/h.
- Use the CSV or PDF buttons to save your result record.
Frequently Asked Questions
1. What is mass flow rate?
Mass flow rate is the amount of mass passing through a section each second. Engineers usually express it in kg/s, kg/h, lb/s, or tons per hour.
2. When should I use the area and velocity method?
Use it when fluid density, average velocity, and cross-sectional area are known. It is common for ducts, nozzles, channels, manifolds, and process equipment sizing.
3. When is the volumetric flow method better?
It is better when a flowmeter already provides volumetric flow. You only need density to convert that value into mass flow quickly and consistently.
4. Why does the gas method need absolute pressure?
Ideal gas density calculations require absolute pressure, not gauge pressure. Using gauge pressure alone can understate density and produce incorrect mass flow values.
5. What does Reynolds number tell me?
Reynolds number helps classify flow as laminar, transitional, or turbulent. That insight is useful when evaluating friction losses, mixing behavior, and instrumentation performance.
6. Can I use this calculator for liquids and gases?
Yes. The direct, volumetric, and pipe methods work for both when density is known. The ideal gas method is intended specifically for gas streams.
7. Which units are supported?
The calculator supports common engineering units for density, velocity, area, diameter, volumetric flow, pressure, temperature, and viscosity, then returns multiple mass flow outputs.
8. Why are my results different from plant data?
Differences can come from unsteady flow, wrong density assumptions, gauge versus absolute pressure mistakes, temperature drift, instrument calibration errors, or profile effects.