💨Gas Law Calculator
Solve before/after two-state gas problems — pick your law and enter the known values.
Use this for before/after two-state problems at held-constant conditions. For relating P, V, n, and T directly with a single state, use the Ideal Gas Law Calculator instead.
Free Gas Law Calculator
Working through a before-and-after gas problem — pressure changing at constant temperature, or volume changing as temperature rises? Our free gas law calculator covers Boyle's, Charles's, Gay-Lussac's, Avogadro's, and the Combined Gas Law in one place. Pick the law that matches your held-constant conditions, enter your known state 1 and state 2 values, and solve for whatever's missing.
All common pressure, volume, and temperature units are supported with automatic conversion, and temperature is always checked against absolute zero. Every answer comes with the specific law's formula shown, rearranged and substituted with your numbers.
Built for chemistry and physics coursework, it runs entirely in your browser. No sign-up, no downloads, no limits.
About the Gas Law Calculator
Features
Five laws in one tool
Pick the law matching your problem's held-constant conditions.
Solve for any missing variable
Leave one value blank across the two states and it's solved.
Unit conversion
Common pressure, volume, and temperature units, auto-converted.
Absolute-zero validation
Temperatures below 0 K are rejected as physically impossible.
Frequently Asked Questions
Which gas laws does this cover?
Boyle's, Charles's, Gay-Lussac's, Avogadro's, and the Combined Gas Law.
How is this different from the Ideal Gas Law Calculator?
This tool solves before/after two-state problems at constant conditions; the Ideal Gas Law Calculator relates P, V, n, and T directly with a single state.
Is it free?
Completely free, no sign-up, downloads, or limits.
What units are supported?
Pressure (atm, kPa, mmHg, bar, psi), volume (L, mL, m³, ft³), and temperature (°C, °F, K), all auto-converted.
Does it convert Celsius to Kelvin automatically?
Yes, temperature is always converted to Kelvin internally before solving.
How do I know which law to use?
Pick the law matching what's held constant in your problem (e.g. Boyle's for constant temperature).
Does it show the steps?
Yes, the specific law's rearranged formula with substituted values is shown.
What if I enter a temperature below absolute zero?
It's rejected as physically impossible.
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.