Physics

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Gay-Lussac's Law Calculator.

Solve pressure and temperature at constant volume.

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Set your values

Results update as you type.

02 / ANSWER

Initial pressure

Initial temperature

Final temperature

Final pressure

0.000000Pa

Results update automatically as you type.

Use Cases

Predict pressure change in a rigid container

Determine how the pressure of a gas in a sealed, fixed-volume container changes when the temperature changes, useful for safety and design.

Example: If a gas at 100 kPa and 300 K is heated to 350 K, the final pressure is 116.67 kPa.

Find required temperature for a target pressure

Given a desired final pressure, you can rearrange the law to solve for the needed temperature, but this calculator only solves for final pressure with given temperatures.

Frequently Asked Questions

What is Gay-Lussac's Law?: Gay-Lussac's Law states that for a fixed amount of gas at constant volume, pressure is directly proportional to absolute temperature. Mathematically, P1/T1 = P2/T2, where P is pressure and T is temperature in kelvins.
How do I use this calculator?: Enter the initial pressure (Pa), initial temperature (K), and final temperature (K). The calculator will compute the final pressure using the formula P2 = P1 * (T2/T1). Ensure temperatures are in kelvins.
Why must temperature be in kelvins?: Gay-Lussac's Law requires absolute temperature because it is based on the kinetic theory of gases. Using Celsius or Fahrenheit would give incorrect results, as zero on those scales does not represent zero molecular motion.

Tips & Common Mistakes

Tips

Always convert temperatures to kelvins before using the calculator. Add 273.15 to Celsius values.
Ensure the volume remains constant; this law does not apply if the container expands or contracts.
Use consistent units for pressure (Pa) and temperature (K) to get accurate results.
For real gases, this law is an approximation; it works best at low pressures and high temperatures.

Common Mistakes to Avoid

Forgetting to convert Celsius to kelvins, leading to incorrect pressure ratios.
Using gauge pressure instead of absolute pressure; the law requires absolute pressure.
Assuming the law applies when volume changes; it only holds for constant volume.

Last updated: August 13, 2026

Use Cases

Predict pressure change in a rigid container

Determine how the pressure of a gas in a sealed, fixed-volume container changes when the temperature changes, useful for safety and design.

Example: If a gas at 100 kPa and 300 K is heated to 350 K, the final pressure is 116.67 kPa.

Find required temperature for a target pressure

Given a desired final pressure, you can rearrange the law to solve for the needed temperature, but this calculator only solves for final pressure with given temperatures.

Frequently Asked Questions

What is Gay-Lussac's Law?

Gay-Lussac's Law states that for a fixed amount of gas at constant volume, pressure is directly proportional to absolute temperature. Mathematically, P1/T1 = P2/T2, where P is pressure and T is temperature in kelvins.

How do I use this calculator?

Enter the initial pressure (Pa), initial temperature (K), and final temperature (K). The calculator will compute the final pressure using the formula P2 = P1 * (T2/T1). Ensure temperatures are in kelvins.

Why must temperature be in kelvins?

Gay-Lussac's Law requires absolute temperature because it is based on the kinetic theory of gases. Using Celsius or Fahrenheit would give incorrect results, as zero on those scales does not represent zero molecular motion.

Tips & Common Mistakes

Tips

Always convert temperatures to kelvins before using the calculator. Add 273.15 to Celsius values.
Ensure the volume remains constant; this law does not apply if the container expands or contracts.
Use consistent units for pressure (Pa) and temperature (K) to get accurate results.
For real gases, this law is an approximation; it works best at low pressures and high temperatures.

Common Mistakes to Avoid

Forgetting to convert Celsius to kelvins, leading to incorrect pressure ratios.
Using gauge pressure instead of absolute pressure; the law requires absolute pressure.
Assuming the law applies when volume changes; it only holds for constant volume.

Use Cases

Predict pressure change in a rigid container

Determine how the pressure of a gas in a sealed, fixed-volume container changes when the temperature changes, useful for safety and design.

Example: If a gas at 100 kPa and 300 K is heated to 350 K, the final pressure is 116.67 kPa.

Find required temperature for a target pressure

Given a desired final pressure, you can rearrange the law to solve for the needed temperature, but this calculator only solves for final pressure with given temperatures.

Frequently Asked Questions

What is Gay-Lussac's Law?

How do I use this calculator?

Why must temperature be in kelvins?

Tips & Common Mistakes

Tips

Always convert temperatures to kelvins before using the calculator. Add 273.15 to Celsius values.
Ensure the volume remains constant; this law does not apply if the container expands or contracts.
Use consistent units for pressure (Pa) and temperature (K) to get accurate results.
For real gases, this law is an approximation; it works best at low pressures and high temperatures.

Common Mistakes to Avoid

Forgetting to convert Celsius to kelvins, leading to incorrect pressure ratios.
Using gauge pressure instead of absolute pressure; the law requires absolute pressure.
Assuming the law applies when volume changes; it only holds for constant volume.