Five gas laws, one panel.
Pick a mode below — mix and match units freely, everything recalculates live as you type, and every result shows the formula it used.
Solving for P₂ — enter the volume it ends up at.
Solving for V₂ — enter the pressure it ends up at.
Solving for V₂ — enter the temperature it ends up at.
Solving for T₂ — enter the volume it ends up at.
Solving for P₂ — enter the temperature it ends up at.
Solving for T₂ — enter the pressure it ends up at.
Number of moles of gas.
Two or three inputs to an answer.
No manual required — but here's the entire flow in four moves.
Pick a mode
Boyle's, Charles's and Gay-Lussac's Law each hold one variable fixed. Combined lets pressure, volume and temperature all change together. Ideal Gas Law stands alone — no before-and-after needed.
Choose what to solve
Use the segmented switch to pick which value is unknown. The form updates to ask for everything else it needs, and hides the field you're solving for.
Enter what you know
Type a number and pick its unit — mix atm with kPa, or Celsius with kelvin, it's all converted automatically. The example chips fill everything in with one tap.
Read the result
The main answer sits up top with common alternate units below it, and the exact formula with your numbers substituted sits at the bottom. Impossible inputs — negative pressure, absolute zero and below — get flagged instantly.
Five laws, one family of ideas.
Each law fixes one property and relates the other two — the Ideal Gas Law ties all of them together.
Boyle's Law
Constant temperature and amount of gas. Pressure and volume move in opposite directions.
Charles's Law
Constant pressure and amount of gas. Volume rises and falls with absolute temperature.
Gay-Lussac's Law
Constant volume and amount of gas. Pressure rises and falls with absolute temperature.
Combined Gas Law
Constant amount of gas, everything else free to change. Boyle's, Charles's and Gay-Lussac's Laws are special cases of this one.
Ideal Gas Law
R = 0.082057 L·atm/(mol·K). Relates pressure, volume, moles and temperature directly, with no before-and-after state.
Absolute temperature
Every gas law above needs temperature in kelvin — this calculator converts Celsius or Fahrenheit automatically before solving.
Questions people actually ask.
The short answers — with the long ones one tap away.
What is Boyle's Law?+
Boyle's Law says that at constant temperature and amount of gas, pressure and volume are inversely related: P₁V₁ = P₂V₂. Compress a gas into a smaller volume and its pressure rises by the same factor.
What is Charles's Law?+
Charles's Law says that at constant pressure, volume is directly proportional to absolute temperature: V₁/T₁ = V₂/T₂. Temperature has to be in kelvin for the ratio to hold.
What is Gay-Lussac's Law?+
Gay-Lussac's Law says that at constant volume, pressure is directly proportional to absolute temperature: P₁/T₁ = P₂/T₂. Heating a sealed rigid container raises the pressure inside proportionally.
What is the Combined Gas Law?+
The Combined Gas Law merges Boyle's, Charles's and Gay-Lussac's Laws for a fixed amount of gas: P₁V₁/T₁ = P₂V₂/T₂. Use it whenever pressure, volume and temperature all change at once.
What does PV = nRT mean?+
It's the Ideal Gas Law: P is pressure, V is volume, n is moles of gas, T is absolute temperature, and R is the gas constant (0.082057 L·atm per mol·K). It relates all four properties of a gas at once, without needing a before-and-after state.
Why do gas laws need kelvin instead of Celsius?+
Gas laws are ratios built on absolute temperature, where zero really means zero kinetic energy. Celsius and Fahrenheit have arbitrary zero points, so a ratio built on them gives the wrong answer. This calculator converts any temperature unit to kelvin automatically before solving.
Is this tool free, and where does my data go?+
It's completely free and runs entirely in your browser — nothing you type is uploaded, logged, or sent to any server. No account, no sign-up, no limits.