Ideal Gas Law CalculatorCalculator
Solve for pressure (P), volume (V), molar quantity (n), or temperature (T) using the Universal Ideal Gas Law across multiple units.
Gas State Parameters (Solve Any Variable)
Calculated State Results
Ideal Gas Law Calculator - PV = nRT Universal Gas Solver: Solve PV = nRT for pressure, volume, moles, mass, and temperature with universal gas constants. Fast, free, and secure client-side execution in your browser.
How to Use the Ideal Gas Law Calculator
Select Target Variable to Solve
Choose Pressure (P), Volume (V), Moles (n), or Temperature (T).
Input Known State Quantities
Provide values for the other three thermodynamic state variables.
Convert to Absolute Units
Notice automatic internal conversion of temperatures to absolute Kelvin.
Inspect Molar Quantities & Multi-Units
Review pressure in atm, Pa, psi, mmHg, and molar volume in L/mol.
Physics Principles & Thermodynamics Guide
The Ideal Gas Law is the equation of state of a hypothetical ideal gas: PV = nRT. Formulated in 1834 by French engineer Émile Clapeyron, it synthesizes four classical empirical gas laws into a single unified mathematical relationship: Boyle's Law (P ∝ 1/V), Charles's Law (V ∝ T), Avogadro's Law (V ∝ n), and Gay-Lussac's Law (P ∝ T).
In the universal equation, P represents absolute pressure, V is volume, n is the amount of substance in moles, T is absolute temperature measured strictly in Kelvin (K = °C + 273.15), and R is the Universal Gas Constant (R = 8.314 J/(mol·K) or 0.08206 L·atm/(mol·K)).
The ideal gas model assumes two key microscopic approximations: (1) gas molecules possess zero volume (point particles), and (2) no intermolecular forces (attraction or repulsion) act between the molecules. Real gases adhere to ideal gas behavior at high temperatures and low pressures, where molecular kinetic energy vastly exceeds intermolecular forces.
Under Standard Temperature and Pressure (STP, defined as 0°C / 273.15 K and 1 atm / 101.325 kPa), one mole of any ideal gas occupies an identical molar volume of V_m = 22.414 Liters. At Room Temperature and Pressure (RTP, 25°C and 1 atm), molar volume expands to 24.465 Liters.
Key Scientific Advantages
Universal Thermodynamic Solver
Solves for any 1 unknown state variable given the other 3 inputs.
Absolute Temperature Guard
Automatically enforces absolute Kelvin scaling to prevent negative volume errors.
Standard State Benchmarks
One-click presets for STP (0°C, 1 atm) and RTP (25°C, 1 atm).
Avogadro Molecular Counts
Converts molar quantity n into exact molecular counts via Avogadro's constant.
Multi-Unit Pressure Conversions
Simultaneously displays output in atm, Pascals, psi, and mmHg.
Confidential Chemical Modeling
Proprietary gas vessel sizing and chemical reactor math remains 100% private.
Frequently Asked Questions
Gas volume and pressure are directly proportional to absolute thermal kinetic energy, which reaches absolute zero at 0 Kelvin (-273.15°C). Using Celsius would yield impossible negative volumes or division by zero.
STP (Standard Temperature & Pressure) is defined as 0°C (273.15 K) and 1 atm (101.325 kPa), where 1 mole = 22.414 L. RTP (Room Temperature & Pressure) is 25°C (298.15 K) and 1 atm, where 1 mole = 24.465 L.
Real gases deviate under high pressure (where molecular volume cannot be neglected) and low temperature (where intermolecular attraction pulls molecules together). The Van der Waals equation corrects for these effects.
Use R = 0.08206 L·atm/(mol·K) when pressure is in atm and volume is in Liters. Use R = 8.314 J/(mol·K) when working in standard SI units (Pascals and cubic meters).
No. Avogadro's principle dictates that equal volumes of all gases at identical temperature and pressure contain the exact same number of moles, regardless of whether the gas is light helium or heavy sulfur hexafluoride.