STP Calculator (Standard Temperature and Pressure)

Created by Łucja Zaborowska, MD, PhD candidate
Reviewed by Bogna Szyk and Jack Bowater
Last updated: Jan 18, 2024

Chemistry lessons? ⚗️ Our standard temperature and pressure calculator is a simple tool that can make your life easier! Here you can easily compute both the volume and the number of moles of a gas in standard conditions.

Read on to discover the theoretical basis for our calculations – find out what are the standard conditions of temperature and pressure and how to deal with different kinds of chemistry queries based on that subject.

We also recommend checking our molar mass of gas calculator to learn how to determine the molar mass of a gas and the number of moles in it.

What is standard temperature and pressure?

Standard temperature and pressure (STP), a.k.a. standard conditions, describe the environment of a chemical reaction.

Elements that define standard conditions:

  1. The standard temperature is equal to: 273.15 K = 0 °C = 32 °F 🌡️

    Easy to remember – the standard temperature is the freezing point for water!

  2. The standard pressure is equal to: 1 atm = 760 Torr = 760 mm Hg = 101.35 kPa.

    Easy to remember – the standard pressure is equal to 1 atmosphere.

  3. 1 mol of ideal gas in these conditions has a volume of 22.4 liters.

What are the STP conditions used for?

STP conditions are used to compare different sets of data in chemistry. If we describe every reaction like the one that takes place in standard conditions, we can easily see all the differences between them.

How to use our standard temperature and pressure calculator?

Our standard temperature and pressure calculator requires four easy steps:

  1. Enter the volume of the gas.
  2. Enter the temperature at which the process is taking place.
  3. Enter the pressure of the gas.
  4. Your results are here! You will receive both the volume and the number of moles of your substance at standard conditions.

Remember, our calculators work both ways! Whatever it is you're trying to calculate, we're here for you. 😎

How to calculate in standard temperature and pressure?

Standard temperature and pressure (STP) calculations are not as hard as they seem – just follow our example below!

  1. We measured our substance at 350 Kelvins and 850 Torr. Its volume was equal to 5 liters.

    • Our volume [VV] = 5 L;

    • Our temperature [TT] = 350 K; and

    • Our pressure [PP] = 850 Torr.

  2. First, let's calculate the volume of our substance in STP temperature and pressure conditions.

VSTP=V×(273.15/T)×(P/760)\quad\footnotesize V_{\text{STP}} = V\! \times\! (273.15/T)\! \times\! (P/760)

This STP formula uses kelvins, torrs, and liters. Let's add our data:

VSTP=5×(273.15/350)×(850/760)=4.364 L\footnotesize\quad \begin{split} V_{\text{STP}} &= 5\! \times\! (273.15/350)\! \times\! (850/760)\\ &= 4.364\ \text{L} \end{split}
  1. Now, it's time to calculate the number of moles.
MolesSTP=VSTP/22.4=4.364/22.4=0.195\footnotesize\qquad \begin{split} \text{Moles}_{\text{STP}} &= V_{\text{STP}}/22.4\\ &= 4.364/22.4\\ &= 0.195 \end{split}

Formulas used in standard conditions for temperature and pressure

The standard conditions calculations are based on the ideal gas law formula.

PV = nRT

Other equations that might be useful in such situations are:

🎈 Do you already know the difference between an ideal and real gas? If not, check out the Van der Waals equation calculator.


What are the standard conditions of temperature and pressure?

Standard temperature and pressure (STP) means a temperature of 273.15 K (0 °C or 32 °F) and a pressure of 1 atm (101.35 kPa). In practice, this corresponds to the freezing point of pure water at atmospheric pressure at sea level. At STP, one mole of gas occupies exactly 22.4 liters of volume (molar volume).

What is standard temperature and pressure in chemistry?

In chemistry, the standard pressure is exactly 100,000 Pa (1 bar, 14.5 psi, 0.98692 atm). In laboratory conditions, STP is often taken as a temperature of 298.15 K (25 °C, 77 °F) and a standard pressure of exactly 1 atm (101,325 Pa, 1.01325 bar). STPs are commonly used to perform calculations on liquids and gases whose properties are highly dependent on temperature and pressure.

Is 25 °C a standard temperature?

No, the STP (standard temperature and pressure) temperature is 0 °C. Although useful for calculations, it is not practical for most laboratory experiments, so most tables compile data at temperatures of 25 °C.

What is standard pressure in mm Hg?

It's 760 mm Hg, and the STP pressure in other units is equal to 1 atm, 101.35 kPa, or 760 Torr. Note that this is the pressure measured at sea level.

What volume does 5 g of O₂ occupy at STP?

3.5 dm³ or 3.5 liters. Knowing that at STP, a mole of each gas is 22.4 dm³:

  1. Calculate molar mass of O₂: 2 × 16 g/mol = 32 g/mol.

  2. Find the number of moles of O₂: 5 g / 32 g = 0.156 moles.

  3. One mole is 22.4 dm³, so 0.156 moles will be 0.156 × 22.4 dm³ = 3.5 dm³.

What is difference between STP and NTP?

STP corresponds to standard pressure and temperature, while NTP stands for normal pressure and temperature. The STP pressure and temperature values for a gas are 273.15 K and 1 atm, respectively. The NTP pressure and temperature values are 293.15 K and 1 atm, respectively.

Łucja Zaborowska, MD, PhD candidate
In standard conditions:
No. of moles
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