# What is the difference between STP and NTP?

May 1, 2014

STP stands for Standard Temperature and Pressure, and NTP stands for Normal Temperature and Pressure.

#### Explanation:

STP stands for Standard Temperature and Pressure.
NTP stands for Normal Temperature and Pressure.

STP is set by the IUPAC as 0°C and 100 kPa or 1 bar.

Many old books and online sources say that standard pressure is 101.325 kPa (the old IUPAC standard that was changed in 1982), but I defer to the current IUPAC standard of 100 kPa.

NTP is set at 101.325 kPa but uses 20°C as the temperature.

Note:
0°C = 273.15K
20°C = 293.15K

In simple language:

STP stands for Standard Temperature and Pressure.
NTP stands for Normal Temperature and Pressure.

At STP: $\textcolor{w h i t e}{l} \text{Pressure = 1 bar = 0.987 atm}$
$\textcolor{w h i t e}{m m m l l} \text{Temperature = 273 K or 0°C}$

At NTP: $\text{Pressure = 1 atm}$
$\textcolor{w h i t e}{m m m l l} \text{Temperature = 293 K or 20°C}$

Also,
1 atm = 1.013 bar
1 atm = 76.0 cm
1 atm = 0.760 m

Here,
cm = centimetre
m = metre
atm = atmosphere