ALWAYS use liters, Degrees Kelvin and pressure in torr for these calculations.

For an STP Calculator With More Input Options Click Here

Gas volumes are compared at a Standard Temperature and Pressure of:
273.15° Kelvin and 760 torr.
At STP, one mole of any gas should
have a volume of 22.4 liters.

Here is an example of determining volume at Standard Temperature and Pressure and the number of moles of gas in a given volume.

2 liters of a gas at 546.3 Degrees Kelvin and a pressure of 380 torr will have what volume and contain how many moles at Standard Temperature and Pressure?
(Your answer should be .5 liters and 0.022321 moles)

The default setting is for 5 significant figures but you can change that by inputting another number in the box above.

Answers are displayed in scientific notation and for easier readability, numbers between .001 and 1,000 will be displayed in standard format (with the same number of significant figures.)
The answers should display properly but there are a few browsers that will show no output whatsoever. If so, enter a zero in the box above. This eliminates all formatting but it is better than seeing no output at all.