Enter your gas's Volume, Temperature, and Pressure into the STP Calculator to find the Volume at STP, along with the Number of Moles and Number of Molecules — add an optional Molar Mass or Mass to also calculate your gas's Density at STP.
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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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.
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.
At STP conditions, one mole of any ideal gas occupies 22.4 liters. This is known as the molar volume of gas at STP.
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.
To convert Celsius to Kelvin, add 273.15 to the Celsius temperature. For example, 25°C = 25 + 273.15 = 298.15 K.
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.
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.
Multiply the number of moles by Avogadro's number (6.022 × 10²³). This gives you the total number of molecules in the gas sample.