STP Calculator

STP (Standard Temperature and Pressure) is a reference condition used in chemistry to compare gas behavior — 0°C and 1 atm — and the STP Calculator converts a gas sample from any conditions to its equivalent volume at STP. Enter the gas's volume, temperature, and pressure to get the volume at STP. Optionally, add molar mass and mass to also calculate the number of moles, density at STP, and number of molecules.

L
K
mmHg
g/mol

Required for mass calculations

g

Required for moles calculation

Results

Volume at STP

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Number of Moles

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Density at STP

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Number of Molecules

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Frequently Asked Questions

What is standard temperature and pressure (STP)?

STP refers to standard conditions of 273.15 K (0°C) temperature and 1 atmosphere (760 mmHg) pressure. These conditions are used as a reference point for gas calculations in chemistry.

How do you calculate volume at STP?

Volume at STP is calculated using the formula: V_STP = V × (273.15/T) × (P/760), where V is the original volume, T is temperature in Kelvin, and P is pressure in mmHg.

What volume does one mole of gas occupy at STP?

At STP conditions, one mole of any ideal gas occupies 22.4 liters. This is known as the molar volume of gas at STP.

Why is STP important in chemistry calculations?

STP provides a standard reference point that allows chemists to compare gas properties under consistent conditions. It simplifies calculations and makes it easier to predict gas behavior.

How do you convert temperature to Kelvin for STP calculations?

To convert Celsius to Kelvin, add 273.15 to the Celsius temperature. For example, 25°C = 25 + 273.15 = 298.15 K.

What is the difference between STP and SATP?

STP uses 0°C and 1 atm, while SATP (Standard Ambient Temperature and Pressure) uses 25°C and 1 atm. SATP is more commonly used in modern chemistry as it represents typical laboratory conditions.

Can this calculator be used for real gases?

This calculator assumes ideal gas behavior, which is accurate for most gases at STP conditions. Real gases may deviate slightly from these calculations, especially at high pressures or low temperatures.

How do you calculate the number of molecules from moles?

Multiply the number of moles by Avogadro's number (6.022 × 10²³). This gives you the total number of molecules in the gas sample.