Interactive Gas Law Calculator
Choose a gas law, select the unknown variable, then enter the known values to solve instantly.
What this gas law calculator helps you do
This gas law calculator is built for quick science and engineering problem-solving. It handles the most common gas equations in one place: Boyle's Law, Charles's Law, Gay-Lussac's Law, the Combined Gas Law, and the Ideal Gas Law. Instead of rearranging formulas by hand every time, you can pick the variable you need and compute it directly.
It is useful for students in chemistry and physics, lab technicians, and anyone reviewing thermodynamics fundamentals.
Quick refresher on the core gas laws
1) Boyle's Law
At constant temperature and amount of gas, pressure and volume are inversely related:
P₁V₁ = P₂V₂
- If volume decreases, pressure rises.
- If volume increases, pressure falls.
2) Charles's Law
At constant pressure and amount of gas, volume is directly proportional to absolute temperature:
V₁/T₁ = V₂/T₂
- Heating a gas increases volume.
- Cooling a gas decreases volume.
3) Gay-Lussac's Law
At constant volume and amount of gas, pressure is directly proportional to absolute temperature:
P₁/T₁ = P₂/T₂
- Higher temperature leads to higher pressure in a fixed container.
4) Combined Gas Law
When pressure, volume, and temperature can all change (with constant moles):
P₁V₁/T₁ = P₂V₂/T₂
5) Ideal Gas Law
The broad relationship linking pressure, volume, temperature, and moles:
PV = nRT
In this calculator, R = 0.082057 L·atm/(mol·K).
How to use this calculator correctly
- Select the gas law that matches your problem setup.
- Pick the variable you want to solve for.
- Enter all known values in consistent units.
- For any temperature variable (T), use Kelvin, not Celsius.
- Click Calculate.
Unit and temperature tips
Most calculation errors come from unit mismatch. Keep units consistent through each equation.
- Pressure: atm, kPa, or mmHg (use one unit consistently)
- Volume: L or mL (convert if necessary)
- Temperature: always convert to Kelvin for gas law equations
Kelvin conversion: K = °C + 273.15
Example use cases
Example A: Boyle's Law
A gas has P₁ = 1.20 atm and V₁ = 2.00 L. It is compressed to V₂ = 1.50 L. Solve for P₂.
The calculator returns P₂ = 1.60 atm.
Example B: Ideal Gas Law
Given n = 0.50 mol, T = 300 K, and V = 10.0 L, solve for pressure P.
The calculator returns P ≈ 1.23 atm.
Common mistakes to avoid
- Using Celsius directly in formulas that require Kelvin.
- Forgetting to use matching pressure/volume units for the chosen R constant.
- Entering zero or negative values for temperature in Kelvin.
- Mixing states (state 1 vs state 2) in Combined Gas Law problems.
Final note
This tool is ideal for practice, homework checks, and quick lab estimates. For graded work, always show your setup, units, and intermediate steps so your method is clear and easy to verify.