How this calculation works
The ideal gas law uses absolute temperature in kelvin and the molar gas constant R = 8.31446261815324 J/(mol·K). Volume in cubic metres yields pressure in pascals.
Pressure = n × R × absolute temperature ÷ volumeA worked example
1 mol at 300 K in 0.025 m³ gives approximately 99,773.551418 Pa.
Good to know
Ideal-gas approximation. Real-gas deviations can matter, especially near condensation, at high pressure or low temperature.
Temperature must start from absolute zero
In the ideal gas equation, pressure is proportional to absolute temperature when amount and volume stay fixed. Doubling temperature in kelvin doubles the modeled pressure. Doubling a Celsius reading does not generally represent the same physical change.
For example, 300 K to 600 K doubles the absolute temperature. The corresponding Celsius values are about 26.85°C and 326.85°C, which plainly are not in a two-to-one ratio.
Volume and pressure must match the chosen gas constant
The constant used here is expressed in joules per mole per kelvin. With amount in moles, temperature in kelvin and volume in cubic metres, pressure comes out in pascals. Mixing litres into the volume field without conversion creates a factor-of-1,000 error.
The ideal model ignores real-gas interactions and finite molecular volume. It is not a pressure-vessel design or a substitute for real-gas data when those effects matter.
A few questions, answered
Is the pressure absolute or gauge?
The ideal gas law uses absolute pressure. Gauge pressure is relative to an external reference and is not the direct output here.
Can I enter Celsius?
Convert to kelvin by adding 273.15 first.