What is the Combined Gas Law Calculator?
The combined gas law relates initial and final states of a fixed amount of gas: P₁V₁/T₁ = P₂V₂/T₂. It merges Boyle's law (P–V), Charles's law (V–T), and Gay-Lussac's law (P–T). Enter five of the six values and solve for the sixth — any of P₁, V₁, T₁, P₂, V₂, or T₂. Supports atm, kPa, mmHg, Pa; L and mL; kelvin and Celsius. Runs instantly in your browser with no signup.
How to use the Combined Gas Law Calculator
- Choose which variable to solve.
- Enter the five known initial and final P, V, and T values.
- Select pressure, volume, and temperature units.
- Read the solved value and the full P₁V₁/T₁ = P₂V₂/T₂ breakdown.
- Copy the summary for homework or lab notes.
Common use cases
- Finding final pressure when T doubles at constant volume
- Calculating V₂ when P doubles and T stays constant (Boyle limit)
- Predicting gas state after simultaneous P, V, and T changes
Frequently asked questions
- What is the combined gas law?
- P₁V₁/T₁ = P₂V₂/T₂ for a fixed amount of gas. It describes how pressure, volume, and temperature change together between two states.
- How is it different from the ideal gas law?
- The ideal gas law (PV = nRT) includes moles and finds one variable from three. The combined gas law compares two states when n is constant — no R needed.
- When does it reduce to Boyle's or Charles's law?
- If T is constant, it becomes P₁V₁ = P₂V₂ (Boyle). If P is constant, it becomes V₁/T₁ = V₂/T₂ (Charles).
- Must temperature be in kelvin?
- Yes internally. Enter °C and the calculator converts to kelvin before solving.
