PV = nRT Calculator
Choose the variable you want to solve, enter the other three values, then click calculate.
What Is the Ideal Gas Equation?
The ideal gas equation is one of the most important relationships in introductory chemistry and physics: PV = nRT. It connects pressure, volume, amount of gas, and temperature in a single compact formula. This calculator helps you quickly solve for any one variable when the other three are known.
The equation assumes an “ideal” gas, meaning particles have negligible volume and do not attract each other. Real gases deviate from this behavior at very high pressures or very low temperatures, but for many classroom and practical engineering calculations, the ideal approximation works very well.
Meaning of Each Variable
- P = Pressure
- V = Volume
- n = Amount of gas in moles
- R = Universal gas constant (8.314462618 J/mol·K)
- T = Temperature in absolute scale (Kelvin in the core equation)
How to Use This Ideal Gas Equation Calculator
Step 1: Select your unknown
Pick whether you want to solve for pressure, volume, moles, or temperature.
Step 2: Enter the known values
Fill in the remaining three values and choose matching units for pressure, volume, and temperature. The tool automatically converts everything to SI units internally before calculating.
Step 3: Calculate and read the result
Click the calculate button to get your answer in the currently selected unit for that variable. You’ll also see the exact rearranged form of the equation used in the computation.
Common Rearrangements of PV = nRT
- P = nRT / V
- V = nRT / P
- n = PV / RT
- T = PV / nR
Worked Example
Suppose you have 1.50 mol of gas in a 10.0 L container at 25°C. What is the pressure? Convert temperature to kelvin (298.15 K), convert 10.0 L to 0.0100 m³, and apply: P = nRT/V.
The result is approximately 371,700 Pa, or about 371.7 kPa. This is exactly the kind of problem the calculator handles in one click.
Tips to Avoid Mistakes
- Do not use negative absolute temperatures (below 0 K is non-physical).
- Be careful with liters vs cubic meters (1 m³ = 1000 L).
- Keep pressure and volume units consistent when doing manual work.
- Use enough significant figures when intermediate steps are sensitive.
When the Ideal Model Is Less Accurate
The ideal model can break down for dense gases, high pressures, and low temperatures. In those cases, equations like Van der Waals or compressibility-factor methods may be better. Still, PV = nRT remains the best first-pass estimate and a foundational scientific tool.