ideal gas law formulas and interpretation
The ideal gas law connects pressure, volume, amount of substance, and absolute temperature.
The calculator preserves all four unknown-variable modes and common pressure, volume, and temperature conversions.
How to use the ideal gas law calculator
- Choose a model: Select the relationship matching the problem.
- Choose the unknown: Select the quantity to calculate.
- Enter values: Enter all known values with matching units and signs.
- Calculate: Review the result, formula, units, and direction.
Formula and variables
Pressure times volume equals moles times the molar gas constant times absolute temperature.
PV = nRT- P — Pressure
- Absolute gas pressure (Pa)
- V — Volume
- Gas volume (m³)
- n — Amount
- Amount of gas (mol)
- R — Gas constant
- Molar gas constant (J/(mol·K))
- T — Temperature
- Absolute temperature (K)
One mole example
One mole of ideal gas occupies 0.024 m³ at 300 K.
- Moles
- 1 mol
- Volume
- 0.024 m³
- Temperature
- 300 K
- P = nRT/V
- P ≈ 103,931 Pa
Result: Pressure is about 104 kPa.
The value is close to atmospheric pressure.
Understanding your results
Interpreting the result
Use absolute pressure and kelvin; real gases deviate most at high pressure and near condensation.
Assumptions
- The selected equation represents the physical system.
- Inputs use a consistent reference direction.
- Values are converted through coherent SI units.
Limitations
- Vector components must be resolved along a common axis.
- External forces or energy losses are not added automatically.
- Results depend on the accuracy of entered measurements.
Common mistakes
- Mixing incompatible units.
- Dropping negative signs that represent direction.
- Using weight where mass is required.
- Entering a zero divisor.
Practical use cases
Physics problems
Check classroom, laboratory, and mechanics calculations.
Practical estimates
Estimate motion, forces, and energy for real systems.
Frequently asked questions
Can a result be negative?
Yes. For directional quantities, the sign indicates direction relative to the chosen positive axis.
Should I use SI units?
The interface can convert supported units, while the formulas are evaluated through coherent SI units.
Sources and review
- SI Brochure, 9th edition — BIPM. Accessed 2026-07-11.
- Special Publication 811 — NIST. Accessed 2026-07-11.
Reviewed 2026-07-11.