Mass Flux Density Converter
Convert mass flux density, the mass flowing per unit of area per unit of time, between kilograms or grams per second or hour per square meter, square centimeter or square foot, and pounds per hour or second per square foot.
Select two units to see the conversion factor.
Mass flux density is mass per area per time. Liquid flux in L/(m²·h) is a volume flux and needs the fluid density to convert.
Mass Flux Density Formula
Every mass flux density unit is a mass divided by an area and a time, so each one is a fixed multiple of one reference unit, the kilogram per second per square meter (kg/(s·m²)). To convert, multiply the value by the size of the source unit in kg/(s·m²), then divide by the size of the target unit in kg/(s·m²). Mass, area and time scale together: 1 lb = 0.45359237 kg, 1 ft² = 0.09290304 m², 1 cm² = 10⁻⁴ m², 1 h = 3,600 s.
What Is Mass Flux Density?
Mass flux density, also called mass flux or mass velocity, is the mass of material that passes through a unit of area in a unit of time. In symbols it is the mass flow rate divided by the cross-sectional area, G = ṁ ÷ A, and its SI unit is the kilogram per second per square meter (kg/(s·m²)). For a fluid flowing through a pipe it also equals the density multiplied by the average velocity, G = ρ × v.
Because the area is part of the unit, mass flux density tells you how concentrated a flow is, not just how much there is. Ten kilograms per second spread over a large duct gives a low mass flux, while the same flow squeezed through a small nozzle gives a very high one. Engineers use it to size packed columns and filters, to compare evaporation and drying rates and to describe heat- and mass-transfer equipment.
Mass flux density should not be confused with mass flow rate (mass per time only), with volumetric flux in L/(m²·h) (volume per area per time) or with heat flux. Only the mass-based units listed below are converted here.
Supported Units
This converter supports the following 7 mass flux density units. The last column shows how many kg/(s·m²) one unit equals. Because the area unit changes along with the mass and time units, the factors can look large: one gram per second per square centimeter is 10 kg/(s·m²), since a square meter holds 10,000 square centimeters.
| Unit | Symbol | Value in kg/(s·m²) |
|---|---|---|
| Gram per second per square meter | g/(s·m²) | 0.001 |
| Kilogram per hour per square meter | kg/(h·m²) | 0.0002777777778 |
| Kilogram per hour per square foot | kg/(h·ft²) | 0.002989975116 |
| Kilogram per second per square meter | kg/(s·m²) | 1 |
| Gram per second per square centimeter | g/(s·cm²) | 10 |
| Pound per hour per square foot | lb/(h·ft²) | 0.001356229899 |
| Pound per second per square foot | lb/(s·ft²) | 4.882427636 |
How to Use the Mass Flux Density Converter
- Type the mass flux density in the value box. Decimals and scientific notation such as 0.0025 or 2.5e-3 are accepted.
- Choose the From unit and the To unit.
- The result appears instantly, or press Convert Now. Very large or very small results are shown in scientific notation.
- Use Swap Units to reverse the conversion, Copy Result to copy the answer, open Show this value in all units for a full list, and Clear to start again.
Step-by-step by hand
- Find the size of each unit in the common base unit (kg/(s·m²)): 1 kg/(h·m²) = 0.0002777777778 kg/(s·m²) and 1 lb/(h·ft²) = 0.001356229899 kg/(s·m²).
- Divide the source size by the target size to get the conversion factor: 0.0002777777778 ÷ 0.001356229899 = 0.2048161436, so 1 kg/(h·m²) = 0.2048161436 lb/(h·ft²).
- Multiply by your value: 10 kg/(h·m²) × 0.2048161436 = 2.048161436 lb/(h·ft²).
Mass flux density cannot be negative here, so only zero and positive numbers are accepted.
Common Mass Flux Density Conversions
- Drying and evaporation: an evaporation rate of 2.5 kg/(h·m²) equals 0.6944444444 g/(s·m²) and 0.5120403591 lb/(h·ft²).
- Laboratory bench data: 0.05 g/(s·cm²) equals 0.5 kg/(s·m²).
- Imperial equipment data: 500 lb/(h·ft²) equals 2,441.213818 kg/(h·m²) and 0.6781149495 kg/(s·m²).
- Mass velocity: 1 lb/(s·ft²) equals 4.882427636 kg/(s·m²).
- Per square foot to per square meter: 100 kg/(h·ft²) equals 1,076.391042 kg/(h·m²).
- Check by pipe flow: a fluid of density 1,000 kg/m³ moving at 2 m/s has G = 1,000 × 2 = 2,000 kg/(s·m²).
Mass Flux Density Conversion – Common Values
Quick reference for frequently used values
| kg/(h·m²) | g/(s·m²) | kg/(s·m²) | lb/(h·ft²) | lb/(s·ft²) |
|---|---|---|---|---|
| 0.1 | 0.02777777778 | 2.777777778e-5 | 0.02048161436 | 5.689337323e-6 |
| 1 | 0.2777777778 | 0.0002777777778 | 0.2048161436 | 5.689337323e-5 |
| 5 | 1.388888889 | 0.001388888889 | 1.024080718 | 0.0002844668661 |
| 10 | 2.777777778 | 0.002777777778 | 2.048161436 | 0.0005689337323 |
| 50 | 13.88888889 | 0.01388888889 | 10.24080718 | 0.002844668661 |
| 100 | 27.77777778 | 0.02777777778 | 20.48161436 | 0.005689337323 |
| 500 | 138.8888889 | 0.1388888889 | 102.4080718 | 0.02844668661 |
| 1,000 | 277.7777778 | 0.2777777778 | 204.8161436 | 0.05689337323 |
| 3,600 | 1,000 | 1 | 737.338117 | 0.2048161436 |
| 10,000 | 2,777.777778 | 2.777777778 | 2,048.161436 | 0.5689337323 |
Where and Why This Conversion Is Used
- Chemical engineering: mass velocity in packed towers, absorbers and strippers is quoted in kg/(s·m²) or lb/(h·ft²) and often compared with flooding limits.
- Drying, evaporation and humidification: drying rate and evaporation flux are expressed per unit of exposed area.
- Heat exchangers and boilers: mass velocity through tubes controls pressure drop and heat-transfer coefficients.
- Filtration and separation: solids loading and throughput per unit filter area are given as mass flux.
- Combustion and fluidised beds: burning and feed rates per area of grate or bed.
- Textbooks and data sheets: older and US sources use lb/(h·ft²), modern SI sources use kg/(s·m²) or g/(s·m²).
For total mass per time without area see the Flow - Mass Converter, and for volume per time use the Flow Converter.