Volume occupied by a unit of mass (inverse of density).
Please enter a valid positive number.
Calculated Mass (Weight)
10,000kg
Formula: Mass = Volume / Specific Volume
Mass in Pounds (lbs)–
Calculated Density (ρ)–
Weight Force (Earth Gravity)–
Mass vs. Volume Scenario
Comparison of calculated mass against standard water density for increasing volumes.
Volume Variation Table
Volume
Calculated Mass
Equivalent Force (N)
Table showing mass variations based on ±50% of input volume.
What is Calculate Weight from Specific Volume?
To calculate weight from specific volume is a fundamental engineering task used to determine the mass of a substance within a container or system based on its thermodynamic properties. Specific volume is an intrinsic property representing the volume occupied by a unit of mass of a substance. It is the reciprocal of density.
Engineers, HVAC technicians, and chemists frequently use this calculation when dealing with gases, steam, and liquids where specific volume changes significantly with temperature and pressure. Unlike simple density calculations, working with specific volume is often required when using steam tables or thermodynamic charts.
Note: While the term "weight" is often used colloquially, this calculator primarily determines mass. Weight is technically the force of gravity acting on that mass. Our tool provides both values for complete accuracy.
Calculate Weight from Specific Volume Formula
The mathematical relationship to derive mass (and subsequently weight) from specific volume is straightforward. Since specific volume ($v$) is defined as Volume ($V$) divided by Mass ($m$), we can rearrange the equation to solve for Mass.
The Core Formula:
$m = \frac{V}{v}$
Where:
$m$ = Mass (kg or lbs)
$V$ = Total Volume ($m^3$ or $ft^3$)
$v$ = Specific Volume ($m^3/kg$ or $ft^3/lb$)
Once the mass is known, the weight force ($W$) can be calculated using Newton's second law ($W = m \times g$), where $g$ is the acceleration due to gravity ($9.81 m/s^2$).
Variable Definitions Table
Variable
Meaning
SI Unit
Imperial Unit
$m$
Mass of substance
Kilograms (kg)
Pounds mass (lbm)
$V$
Total Volume
Cubic Meters ($m^3$)
Cubic Feet ($ft^3$)
$v$
Specific Volume
$m^3/kg$
$ft^3/lb$
$\rho$
Density (1/v)
$kg/m^3$
$lb/ft^3$
Practical Examples (Real-World Use Cases)
Example 1: Steam in a Turbine
A power plant engineer needs to calculate the mass of steam flowing through a pipe section with a volume of 5 $m^3$. From the steam tables, at the current pressure and temperature, the specific volume of the superheated steam is 0.25 $m^3/kg$.
Input Volume ($V$): 5 $m^3$
Specific Volume ($v$): 0.25 $m^3/kg$
Calculation: $m = 5 / 0.25 = 20$ kg
Result: The mass of the steam in that section is 20 kg.
Example 2: HVAC Air Handling
An HVAC technician is analyzing an air duct. The volume of air is 500 cubic feet ($ft^3$). The specific volume of dry air at standard conditions is approximately 13.33 $ft^3/lb$.
Input Volume ($V$): 500 $ft^3$
Specific Volume ($v$): 13.33 $ft^3/lb$
Calculation: $m = 500 / 13.33 \approx 37.51$ lbs
Result: The mass of the air is approximately 37.51 lbs.
How to Use This Calculator
Enter Volume: Input the total physical space the substance occupies. Select the correct unit (Cubic Meters, Liters, Cubic Feet, etc.).
Enter Specific Volume: Input the specific volume value. This is typically found in thermodynamic property tables (like Steam Tables or Refrigerant Tables).
Review Results: The calculator instantly computes the Mass in kilograms.
Check Intermediate Values: Look at the breakdown for pounds (lbs), density, and weight force in Newtons.
Analyze Charts: Use the dynamic chart to visualize how mass would change if the volume were larger or smaller.
Key Factors That Affect Results
When you calculate weight from specific volume, several external factors influence the accuracy and relevance of your results:
Temperature: Specific volume is highly sensitive to temperature. As temperature increases, gases expand, increasing specific volume and decreasing density/weight for a fixed volume.
Pressure: For gases and compressible fluids, increased pressure reduces specific volume (compressing the mass), which increases the total weight within a fixed volume.
Phase of Matter: A substance behaves very differently as a liquid versus a vapor. The specific volume of steam is vastly higher than liquid water, resulting in much lower weight for the same volume.
Measurement Units: Confusing Imperial ($ft^3/lb$) and SI ($m^3/kg$) units is a common error. Always double-check your unit inputs.
Altitude/Gravity: While mass remains constant, "weight" (force) changes slightly with altitude due to gravity variations. This calculator assumes standard Earth gravity ($9.81 m/s^2$).
Impurity/Mixtures: The specific volume provided in tables usually assumes a pure substance. Mixtures (like moist air) require psychrometric calculations to find the correct specific volume.
Frequently Asked Questions (FAQ)
What is the difference between specific volume and density?
They are reciprocals of each other. Density is mass per unit volume ($\rho = m/V$), while specific volume is volume per unit mass ($v = V/m$). If you know one, you can find the other by dividing 1 by the value.
Can I use this for liquids and solids?
Yes. While specific volume is most commonly discussed in thermodynamics for gases and vapors, the physics applies to any state of matter. Solids have very low specific volumes.
Why is my result in kg instead of Newtons?
In standard engineering and commerce, "weight" usually implies mass. However, our intermediate results section provides the Force in Newtons for physics applications.
How do I convert Specific Volume to Density?
Simply calculate $1 / \text{Specific Volume}$. For example, if specific volume is $2 m^3/kg$, density is $0.5 kg/m^3$.
Does specific volume change with humidity?
Yes, for air. Moist air is actually less dense (has a higher specific volume) than dry air at the same temperature, which is counter-intuitive to many.
Is specific volume an intensive or extensive property?
Specific volume is an intensive property because it does not depend on the amount of matter present. Total volume is extensive.
What unit is used for specific volume in the US?
The standard US Customary unit is cubic feet per pound ($ft^3/lb$).
Where can I find specific volume values?
You can find them in engineering reference books, Steam Tables, Refrigerant Property tables (like R-134a or R-410A tables), or chemical handbooks.