BIZOMAT MAKEOS · Pneumatics
Gas Volume at Pressure and Temperature
What volume does this gas occupy at the new pressure and temperature?
Ideal gas conversion of a gas volume or flow between two sets of pressure and temperature, including gauge-to-absolute conversion and free-air to compressed volume.
Open the calculatorRuns in your browser. No account needed.
How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Volume or flow at state 1 | m³ or m³/min | Volume or volume flow at the first condition. |
| Pressure at state 1 (gauge) | bar | Gauge pressure at the first condition (0 for free air). |
| Temperature at state 1 | °C | Temperature at the first condition. |
| Pressure at state 2 (gauge) | bar | Gauge pressure at the second condition. |
| Temperature at state 2 | °C | Temperature at the second condition. |
| Atmospheric pressure | bar | Local atmospheric pressure (1.013 bar at sea level). |
What each input means
Open an input to see what it is, its units, the worked example and the common mistakes, with a small diagram.
What this means: Volume or flow at state 1
- What it is
- The gas volume, or volume flow, at the first set of pressure and temperature conditions. The result is given in the same unit.
- Units and format
- Enter a number in m³ or m³/min: m³ or m³/min. The form accepts 0.000001 m³ or m³/min or more. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 1 m³ or m³/min as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The volume at state 2 scales in direct proportion.
- Get it right
- Keep units consistent: enter a volume to get a volume, or a flow to get a flow.
What this means: Pressure at state 1 (gauge)
- What it is
- The pressure of the gas at the first condition, as read on a gauge. Air at atmospheric pressure reads zero on a gauge.
- Units and format
- Enter a number in bar: bar (1 bar = 100 kPa). The form accepts -1.013 bar to 10000 bar. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0 bar as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A higher starting pressure gives a larger volume at state 2.
- Get it right
- Enter gauge pressure; the tool adds atmospheric pressure to make it absolute.
What this means: Temperature at state 1
- What it is
- The temperature of the gas at the first condition.
- Units and format
- Enter a number in °C: degrees Celsius. The form accepts -273 °C to 3000 °C. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 20 °C as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A higher starting temperature gives a smaller volume at state 2.
- Get it right
- Enter degrees Celsius; the tool converts to kelvin.
What this means: Pressure at state 2 (gauge)
- What it is
- The pressure of the gas at the second condition, as read on a gauge.
- Units and format
- Enter a number in bar: bar (1 bar = 100 kPa). The form accepts -1.013 bar to 10000 bar. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 7 bar as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A higher final pressure gives a smaller volume at state 2.
- Get it right
- Enter gauge pressure; the tool adds atmospheric pressure to make it absolute.
What this means: Temperature at state 2
- What it is
- The temperature of the gas at the second condition.
- Units and format
- Enter a number in °C: degrees Celsius. The form accepts -273 °C to 3000 °C. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 30 °C as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A higher final temperature gives a larger volume at state 2.
- Get it right
- Enter degrees Celsius; the tool converts to kelvin.
What this means: Atmospheric pressure
- What it is
- The local atmospheric pressure, added to both gauge pressures to make them absolute. It falls with altitude and weather.
- Units and format
- Enter a number in bar: bar (1 bar = 100 kPa). The form accepts 0.5 bar to 1.1 bar. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 1.013 bar as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Enter absolute atmospheric pressure in bar; use local data at altitude.
Method and formulas
- Absolute P = gauge + atmospheric; T in kelvin = °C + 273.15.
- V₂ = V₁ × (P₁ ÷ P₂) × (T₂ ÷ T₁).
- Example: 1 m³ of free air at 20 °C occupies 0.13073 m³ at 7 bar g and 30 °C.
Limitations
- Ideal gas; at very high pressures or low temperatures real gases deviate.
- Humidity and condensation are not considered.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Convert free air delivery to compressed volume
- Correct a gas flow to reference conditions
- Estimate the pressure in a heated closed vessel
Who it is for
- Maintenance engineers
- Energy and utilities managers
- Design engineers
What you get
- Volume or flow at state 2
- Absolute pressures and temperatures
- Volume ratio
Interpreting the result
- Always state the reference conditions with a gas volume or flow.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 3032–3041. Topic reference; no source tables or recommended settings are reproduced.
Learn the Concepts Behind This Tool
These BIZOMAT Library readings explain the method this tool uses, with worked examples.
Method explained here · BIZOMAT original book
Metering gas and checking the firing rate
What it covers: What a gas meter measures, correcting metered volumes to standard conditions, turning cubic metres into megajoules, clocking a meter to check a burner's input, and a correction left out.
Method explained here · BIZOMAT original book
Breathing: how enclosures draw in water
In Condensation Control by the Numbers
What it covers: Thermal and barometric breathing, stack flow and cable conduits: how much moist air each path brings into an enclosure, and how a warm, wet pit turned out to be the real source.
Method explained here · BIZOMAT original book
Gas flow and vortex meters
In Flow Measurement by the Numbers
What it covers: Why a gas’s actual volume changes with pressure and temperature, free air and normal volumes, how a vortex meter counts eddies, its low-flow cutoff, and an air audit that understated demand eightfold.
Method explained here · BIZOMAT original book
Plasma nitriding: gas, heat and time
In Plasma Surface Engineering by the Numbers
What it covers: How plasma nitriding hardens steel, how the gas mixture controls the compound layer, what gas flows and power a load needs, and how case depth grows with time.
Method explained here · BIZOMAT original book
The pressure decay test
In Production Leak Testing by the Numbers
What it covers: How a pressure decay test turns a pressure drop into a leak rate, test volume and time, measuring the volume, what the test can resolve, and limits that do not transfer between parts.
BIZOMAT tools are screening and decision-support utilities. Verify important financial, engineering, safety, legal or operational decisions using appropriate professional standards and your organisation’s approved data.