Ideal Gas Law Calculator
Calculate Ideal Gas Law values for science, physics, chemistry, and engineering problems.
This ideal gas law calculator solves PV = nRT for any missing variable - pressure, volume, moles, or temperature - describing how an idealized gas behaves under different conditions.
Enter any three of the four variables, and the calculator solves for the missing one.
Worked Calculation Examples
| Scenario | Result | Calculation Step |
|---|---|---|
| n=2 mol, T=300K, V=10L, solve for P | P ≈ 4.93 atm | P = nRT ÷ V = (2 × 0.0821 × 300) ÷ 10 = 49.26 ÷ 10 ≈ 4.93 atm. |
| P=1 atm, V=22.4L, T=273K, solve for n | n ≈ 1 mol | n = PV ÷ RT = (1 × 22.4) ÷ (0.0821 × 273) ≈ 22.4 ÷ 22.41 ≈ 1.0 mol - this is exactly the classic "1 mole of gas occupies 22.4 L at STP" reference point. |
The Ideal Gas Law Equation
PV = nRT, where P is pressure, V is volume, n is the number of moles of gas, R is the ideal gas constant (0.0821 L*atm/(mol*K) in common units), and T is temperature in Kelvin. Rearranging the formula solves for any single variable when the other three are known.
Why Temperature Must Be in Kelvin
The ideal gas law requires temperature in Kelvin, not Celsius or Fahrenheit, because Kelvin is an absolute temperature scale starting at absolute zero - using Celsius would allow for negative or zero temperature values that break the direct proportional relationship the equation depends on.
How to Use the Ideal Gas Law Calculator
- Open the Ideal Gas Law Calculator and enter the values requested in the input fields.
- Check the units, percentages, dates, or time periods before reading the answer.
- Review the instant result and adjust any value to compare another scenario.
- Use the formula, example, and FAQs below to understand how the ideal gas law calculator works.
Frequently Asked Questions
What is the ideal gas law formula?
PV = nRT, relating pressure (P), volume (V), moles (n), the gas constant (R), and temperature (T) in Kelvin.
Why does the ideal gas law use Kelvin instead of Celsius?
Kelvin is an absolute temperature scale with no negative values, which is necessary for the direct proportional relationships in the ideal gas law to hold true mathematically.
What is the value of the gas constant R?
The most common value is 0.0821 L*atm/(mol*K), though R takes different numeric values depending on which units are used for pressure and volume.
How do I use this ideal gas law calculator?
Enter the known values, review the units or settings, and the calculator updates the result instantly. The formula and example on this page show how the answer is produced.
What does the Ideal Gas Law Calculator calculate?
Calculate Ideal Gas Law values for science, physics, chemistry, and engineering problems. It is designed for fast browser-based calculations without sign-up, downloads, or manual spreadsheet setup.
What formula does this ideal gas law use?
The formula is: PV = nRT. This single equation actually unifies three separate gas laws discovered independently over the preceding century: Robert Boyle's 1662 finding that pressure and volume are inversely related, Jacques Charles's 1780s work relating volume and temperature, and Amedeo Avogadro's 1811 hypothesis relating volume to the number of gas particles - French physicist Émile Clapeyron combined all three into the single ideal gas law in 1834.
Related Calculators
Stoichiometry Calculator
Calculate Stoichiometry values for science, physics, chemistry, and engineering problems.
pH Calculator
Calculate pH values for science, physics, chemistry, and engineering problems.
Half-Life Calculator
Calculate Half-Life values for science, physics, chemistry, and engineering problems.
Wavelength Frequency Calculator
Calculate Wavelength Frequency values for science, physics, chemistry, and engineering problems.
Molarity Calculator
Calculate Molarity values for science, physics, chemistry, and engineering problems.
Dilution Calculator
Calculate Dilution values for science, physics, chemistry, and engineering problems.
Last updated: September 27, 2026.