PV = nRT | Solve for Pressure, Volume, Moles, or Temperature | Gas Law Tool
Result
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š Step-by-step solution
Select variable to solve and enter known values
š” R = 8.314 J/(molĀ·K) = 0.0821 LĀ·atm/(molĀ·K) | Pressure in Pa or atm | Volume in mĀ³ or L | Temp MUST be in Kelvin
š How to Use This Ideal Gas Law Calculator
1
Select what you want to calculate - Pressure (P), Volume (V), Moles (n), or Temperature (T).
2
Enter the known values - For pressure: enter volume, moles, and temperature. For other variables, enter the remaining three values.
3
Click "Calculate" - Get your result with a complete step-by-step solution.
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Important: Temperature must be in Kelvin (K = Ā°C + 273.15). The calculator uses R = 8.314 J/(molĀ·K) for SI units.
š§Ŗ The Ideal Gas Law (PV = nRT)
The ideal gas law is a fundamental equation in chemistry and physics that describes the behavior of an ideal gas. It combines Boyle's Law, Charles's Law, Avogadro's Law, and Gay-Lussac's Law into a single relationship.
P = Pressure (Pa, atm, or other units) V = Volume (mĀ³, L) n = Number of moles (mol) R = Universal gas constant (8.314 J/(molĀ·K) or 0.0821 LĀ·atm/(molĀ·K)) T = Absolute temperature (Kelvin)
š Ideal Gas Law Formulas
Pressure: P = nRT / V Volume: V = nRT / P Moles: n = PV / RT Temperature: T = PV / nR
š¬ Gas Constant R Values
8.314462618 J/(molĀ·K) - SI units (PaĀ·mĀ³/(molĀ·K))
0.082057 LĀ·atm/(molĀ·K) - Common for chemistry (L, atm)
62.3637 LĀ·mmHg/(molĀ·K) - For pressure in mmHg
1.987 cal/(molĀ·K) - Calories version
š” Standard Conditions (STP)
Standard Temperature and Pressure (STP): 0Ā°C (273.15 K) and 1 atm (101,325 Pa)
At STP, 1 mole of ideal gas occupies 22.414 L (molar volume)
Engineering: Pneumatic systems, compressed air calculations
Meteorology: Weather balloon volume predictions at altitude
Medicine: Anesthesia gas mixtures, respiratory therapy
Scuba Diving: Air consumption at depth
ā Frequently Asked Questions (FAQ)
What is an ideal gas vs real gas?
An ideal gas follows PV=nRT perfectly under all conditions. Real gases deviate at high pressure (molecules too close) and low temperature (condensation). The ideal gas law is accurate for most gases at room temperature and atmospheric pressure.
Why must temperature be in Kelvin?
Kelvin is an absolute temperature scale starting at absolute zero (-273.15Ā°C). The ideal gas law requires absolute temperature because pressure and volume are directly proportional to absolute temperature (Charles's Law). Using Celsius would give incorrect results.
Which R value should I use?
Use R = 8.314 for pressure in Pascals (Pa) and volume in cubic meters (mĀ³). Use R = 0.0821 for pressure in atmospheres (atm) and volume in liters (L). This calculator uses SI units (Pa, mĀ³, J/(molĀ·K)).
What does STP mean in chemistry?
STP (Standard Temperature and Pressure) is 0Ā°C (273.15 K) and 1 atm (101.325 kPa). At STP, one mole of an ideal gas occupies 22.414 liters.
How do I convert Celsius to Kelvin?
Kelvin = Celsius + 273.15. For example, 25Ā°C = 298.15 K, 0Ā°C = 273.15 K, -40Ā°C = 233.15 K. Always add 273.15, not 273.
Can I use the ideal gas law for mixtures?
Yes! For gas mixtures, use the total number of moles (sum of all components). The pressure of each gas (partial pressure) follows Dalton's Law: P_total = Pā + Pā + ... and P_i = (n_i / n_total) Ć P_total.