Revised July, 2017
There are now 4 choices for temperature and pressure.

Scroll to the bottom for instructions

For a simpler STP Calculator Click Here

If you have used this calculator previously, the "CALCULATE" button was replaced with "1) IUPAC Pre-1982".
Since there are 22.7109 liters of gas at STP (273.15 K, 750.06 torr) the Number Of Moles Of Gas Equals:

To see how to do STP calculations, click here.
Since gases do not have definite volumes, scientists have agreed upon standard temperatures and pressures at which gas volumes can be compared.

1) Before 1982, the International Union of Pure and Applied Chemistry (IUPAC) defined:
standard temperature as 273.15 Kelvin (0° Celsius) and
standard pressure as 1 standard atmosphere (101,325 Pascals, 760.00 torr).

2) Since 1982, the IUPAC now defines
standard temperature as 273.15 Kelvin (0° Celsius) and
standard pressure as 0.98692 standard atmospheres, 100,000 Pascals, 750.06 torr

3) The National Institute of Standards and Technology (NIST) defines
Normal Temperature and Pressure (NTP) as:
temperature of 293.15 Kelvin (20° Celsius) and
pressure of 1 standard atmosphere (101,325 Pascals, 760.00 torr)

4) Standard Ambient Temperature and Pressure (SATP) is defined as:
temperature of 298.15 Kelvin (25° Celsius) and
pressure of 0.98692 standard atmospheres, 100,000 Pascals, 750.06 torr
This calculator determines STP volume from data that can be input in a wide variety of different units (8 volume units, 4 for temperature and 18 for pressure). It displays the output in liters as well as 7 other volume units.
Also, it will display the number of moles of gas based on 22.711 liters per mole.

Numbers are displayed in scientific format with the option to specify the precision by inputting a number in the box above. For easy readability, numbers between .001 and 1,000 will not be displayed in scientific notation
Internet Explorer and most other browsers, will display the numbers 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.