When to use this calculator
The combined gas law includes both the inverse pressure relationship and the direct absolute-temperature relationship.
Explore the gas laws calculators for other questions in this topic. For a related calculation, use the Daltons Partial Pressure Calculator: Find a gas component’s partial pressure from its mole fraction.
PUTTING IT INTO PRACTICE
Combined Gas Law: a worked example
The values below are an illustrative example, not a recommendation. Replace them with measurements or assumptions that match your question.
| Input | Example value |
|---|---|
| Initial absolute pressure | 2 |
| Initial volume | 3 |
| Initial temperature (K) | 300 |
| Final absolute pressure | 1 |
| Final temperature (K) | 600 |
| Result | 12 input volume units |
- Check the input labels and enter the example values above.
- Apply the relationship: Final volume = initial pressure × initial volume × final temperature/(final pressure × initial temperature).
- The result is 12 input volume units, rounded for display.
How to interpret your result
Assumes a fixed amount of ideal gas and consistent absolute pressure units.
Gas-law ratios require absolute pressure and kelvin temperature. Hold the quantities specified by each law constant. Real gases can depart from ideal behaviour, especially at high pressure or low temperature.
Frequently asked questions
Can I enter Celsius in a gas-law temperature ratio?
No. Convert to absolute temperature in kelvins first. The Celsius zero point is not absolute zero.
When is the combined gas law calculator useful?
The combined gas law includes both the inverse pressure relationship and the direct absolute-temperature relationship.
How do I use the combined gas law calculator?
Enter initial absolute pressure, initial volume, initial temperature (k), final absolute pressure, final temperature (k). The result updates automatically. Use the units shown beside each input; the example values illustrate the method.
Which formula does this calculator use?
Final volume = initial pressure × initial volume × final temperature/(final pressure × initial temperature).
What should I check before using the result?
Assumes a fixed amount of ideal gas and consistent absolute pressure units.
How are results rounded?
Scalar numbers display up to six decimal places, with scientific notation for very large or small values. Text, fraction, date and schedule outputs use the format described on the tool. Intermediate calculations use JavaScript floating-point arithmetic. Keep sensible precision for your measurements.
Further reading
For background on this topic, see OpenStax: gases and the ideal gas law ↗. This is a topic reference, not an external review or endorsement of this tool.
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