STP is the abbreviation for **Standard Temperature and Pressure**. The standard temperature is 273 K (0° Celsius) and the standard pressure is 1 atm pressure. If you perform calculations, it’s useful to know that one mole of gas occupies 22.4 L of volume (molar volume) at STP.

**When Is STP Used?**

You’ll encounter STP in chemistry and physics, when performing calculations involving gases, such as density.

STP is used when *standard state conditions* apply to calculations. You can recognize standard state conditions because they are denoted using the superscript circle. For example, ΔS° is the change in entropy at STP.