The Final Gas Pressure Calculator helps students, engineers, chemists, and lab technicians accurately find the final pressure of a gas after changes in volume, temperature, or amount. It uses the basic gas laws — Boyle’s Law, Gay-Lussac’s Law, the Combined Gas Law, or the Ideal Gas Law — to solve for new pressure conditions. This calculator is essential for chemistry labs, HVAC system checks, scuba tank filling, and any gas storage or transfer operation. It belongs to the Thermodynamics and Gas Laws Calculator category and supports precise calculations for safe and efficient gas handling.
formula of Final Gas Pressure Calculator
1. For constant temperature (Boyle’s Law):
P₂ = (P₁ × V₁) / V₂
Where:
P₁ = initial pressure
V₁ = initial volume
P₂ = final pressure
V₂ = final volume
2. For constant volume (Gay-Lussac’s Law):
P₂ = P₁ × (T₂ / T₁)
Where:
P₁ = initial pressure
T₁ = initial temperature (K)
T₂ = final temperature (K)
P₂ = final pressure
3. For both volume and temperature change (Combined Gas Law):
P₂ = P₁ × (V₁ / V₂) × (T₂ / T₁)
Where:
P₁, V₁, T₁ = initial pressure, volume, and temperature
P₂, V₂, T₂ = final pressure, volume, and temperature
4. If moles change too (full Ideal Gas Law):
P₂ = (n₂ × R × T₂) / V₂
Where:
n₂ = final number of moles
R = universal gas constant (8.314 J/mol·K)
T₂ = final temperature (K)
V₂ = final volume
This version covers all possible changes for ideal gases.
Common Final Gas Pressure Reference Table
Use this table to remember which gas law to apply for different situations.
| Scenario | Recommended Formula | When to Use |
|---|---|---|
| Only volume changes | Boyle’s Law | Gas in a piston with same temp |
| Only temperature changes | Gay-Lussac’s Law | Sealed rigid tank heated or cooled |
| Both volume and temperature change | Combined Gas Law | Inflating balloon in warm/cold air |
| Moles change (gas added/removed) | Ideal Gas Law | Filling a tank or chemical reaction |
This quick guide helps you choose the right formula.
Example of Final Gas Pressure Calculator
Let’s solve a clear example step by step.
Example:
A gas cylinder at 100 kPa and 2 liters is compressed to 1 liter at constant temperature.
- Use Boyle’s Law:
P₂ = (P₁ × V₁) / V₂
= (100 kPa × 2 L) / 1 L
= 200 kPa
So, the final gas pressure is 200 kPa.
Another Example:
A sealed rigid tank at 300 K and 150 kPa is heated to 450 K.
P₂ = P₁ × (T₂ / T₁)
= 150 kPa × (450 K / 300 K)
= 150 kPa × 1.5
= 225 kPa
So, the final pressure after heating is 225 kPa.
Most Common FAQs
Yes! Always use Kelvin for gas laws. Add 273.15 to Celsius to get Kelvin.
These formulas assume an ideal gas. For real mixtures, consider partial pressures and specific interactions for better accuracy.
No. This applies only to gases behaving ideally or close to ideally. Liquids don’t expand and compress like gases.