Case 1
- Fluid density ρ
- 1000kg/m³
- Cross-sectional area A
- 0.01m²
- Flow velocity v
- 2m/s
20.0000kg/s
Open with these valuesMass Flow Rate Calculator
20.0000kg/s
Result: 20.0000 kg/sMass flow rate is density times area times velocity: ṁ = ρ × A × v, in kilograms per second. Water at 2 m/s through a 0.01 m² pipe carries 20 kg/s. The same pipe moves 0.02 m³ of volume per second — density is the only thing between the two figures.
The numbers at a glance
Held fixed: Fluid density ρ 1,000.000000 kg/m³, Cross-sectional area A 0.010000 m².
| Flow velocity v (m/s) | Result (kg/s) |
|---|---|
| 0.000000 | 0.0000 |
| 0.500000 | 5.0000 |
| 1.000000 | 10.0000 |
| 1.500000 | 15.0000 |
| 2.000000Your value | 20.0000 |
| 2.500000 | 25.0000 |
| 3.000000 | 30.0000 |
| 3.500000 | 35.0000 |
| 4.000000 | 40.0000 |
Worked examples
Case 2
- Fluid density ρ
- 1.225kg/m³
- Cross-sectional area A
- 0.5m²
- Flow velocity v
- 10m/s
6.1250kg/s
Open with these valuesCase 3
- Fluid density ρ
- 850kg/m³
- Cross-sectional area A
- 0.0254m²
- Flow velocity v
- 1.5m/s
32.3850kg/s
Open with these valuesHow it's calculated
ṁ = ρ × A × v
- StepEnter the fluid density — water is about 1000, air at sea level about 1.225.
- StepWork out the area the fluid flows through, in square metres.
- ResultEnter the average speed and read the mass passing each second.
Reference table
| ρ, A, v | Fluid | ṁ (kg/s) |
|---|---|---|
| 1000, 0.01, 2 | Water in a pipe | 20 |
| 1.225, 0.5, 10 | Air in a duct | 6.125 |
| 997, 0.0005, 3 | Water, small bore | 1.4955 |
| 13534, 0.002, 0.5 | Mercury | 13.534 |
| 850, 0.0254, 1.5 | Light oil | 32.385 |
Questions
How do I calculate mass flow rate?
Multiply density by cross-sectional area and by flow velocity: ṁ = ρ × A × v. With kg/m³, m² and m/s the answer is in kilograms per second — water through a 0.01 m² pipe at 2 m/s gives 20 kg/s.
What is mass flow rate?
It is the amount of mass passing a cross-section each second, measured in kilograms per second. It is the figure that matters for pipe sizing, pump selection, ventilation and engine design, because it says how much material actually moves rather than how fast.
What is the difference between mass and volumetric flow rate?
Volumetric flow rate measures the volume per second in m³/s, mass flow rate the mass per second in kg/s. The two are linked by density: ṁ = ρ × Q. For gases the density changes with pressure and temperature, so the mass figure is usually the more reliable one.
What units should I use?
Kilograms per cubic metre for density, square metres for area and metres per second for velocity. If your area is in cm², divide by 10 000; if your speed is in km/h, divide by 3.6 before entering it.
What changes the mass flow rate?
All three inputs scale it directly, because the formula multiplies them: double the density, the area or the speed and the mass flow doubles. Where a pipe narrows the speed must rise, which keeps the mass flow rate constant along the pipe.
Sources and last check
Information, not professional advice.