Combined Gas Law Calculator
Solve P₁V₁/T₁ = P₂V₂/T₂ for the final pressure given the initial and final gas states.
How it works
- 1Enter the initial state: pressure P₁ (kPa), volume V₁ (L), and temperature T₁. Toggle metric/imperial to input temperatures in °C or °F.
- 2Enter the final state: volume V₂ (L) and temperature T₂. The calculator solves P₂ = P₁V₁T₂ ÷ (T₁V₂).
- 3The result shows the final pressure P₂ in kPa, with both absolute temperatures in kelvin.
Use cases
- Students solving gas problems where pressure, volume, and temperature all change.
- Estimating a gas sample’s pressure after compression or expansion to a new temperature.
- HVAC and refrigeration — checking a refrigerant’s pressure against measured volume and temperature.
Frequently asked questions
What is the combined gas law formula?
P₁V₁ ÷ T₁ = P₂V₂ ÷ T₂, with T in kelvin. It unifies Boyle’s law (P ∝ 1/V), Charles’s law (V ∝ T), and Gay-Lussac’s law (P ∝ T) into one relationship.
Why must temperature be in kelvin?
The law is a proportional relationship valid only on an absolute scale. Celsius and Fahrenheit have arbitrary zero points that break the proportionality; kelvin measures from absolute zero.
Can you walk me through a worked example?
With P₁ = 100 kPa, V₁ = 2 L, T₁ = 300 K, V₂ = 1 L, T₂ = 600 K: P₂ = (100 × 2 × 600) ÷ (300 × 1) = 400 kPa. Halving the volume and doubling the temperature quadruples the pressure.
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