Frequently Asked Questions
Everything you need to know about the Ideal Gas Law Calculator.
How does the ideal gas law calculator work?
Enter any 3 of pressure, volume, moles, or temperature; it solves PV=nRT for the missing value.
What units are supported?
Pressure in atm, kPa, mmHg, bar, or psi; volume in L, mL, m³, or ft³; temperature in °C, °F, or K.
Which value of R does it use?
The gas constant is automatically matched to your chosen units (e.g. 0.0821 L·atm/mol·K).
Does it convert Celsius to Kelvin automatically?
Yes, temperature is always converted to Kelvin internally before solving.
What happens if I enter a temperature below absolute zero?
It's rejected as physically impossible, with a clear message.
Is there a shortcut for STP problems?
Yes, a toggle sets standard conditions (0°C, 1 atm) automatically.
Does it show the steps?
Yes, unit conversions and the rearranged formula with substituted values are all shown.
Is it free?
Completely free, no sign-up, downloads, or limits.
Is my data stored?
No; everything runs in your browser and isn't stored or sent anywhere.
Does it work on mobile?
Yes, fully responsive on all screen sizes.