How do I convert liters of gas to moles?

At STP (0 °C, 1 atm): moles = liters / 22.414. For arbitrary T and P use the ideal gas law: n = PV / RT, where R = 0.082057 L·atm/(mol·K). Both work for any ideal gas; real-gas corrections (van der Waals) become significant only at very high pressure or very low temperature.

STP has two definitions in current use. The classic chemistry-textbook definition (used in this calculator's default) is 0 °C and 1 atm (101.325 kPa), giving Vₘ = 22.414 L/mol. IUPAC redefined STP in 1997 to 0 °C and 100 kPa (Vₘ = 22.711 L/mol). Many physics texts still use the old definition.

What is the ideal gas law?

PV = nRT. Pressure × Volume = moles × R × Temperature. R = 0.082057 L·atm/(mol·K) = 8.314 J/(mol·K). Discovered piecewise by Boyle (1662), Charles (1787), Gay-Lussac (1809), and Avogadro (1811), then unified by Clapeyron (1834) in the form used today.

What is molar volume?

Molar volume Vₘ is the volume occupied by one mole of gas at specified T, P. Vₘ = V/n. At STP (0 °C, 1 atm) for an ideal gas: Vₘ = RT/P = 0.082057 × 273.15 / 1 = 22.414 L/mol. This number is one of the most-used constants in introductory chemistry.

Why doesn't this work for liquids and solids?

The ideal-gas law assumes negligible particle volume and zero intermolecular forces - true for dilute gases but emphatically not for liquids or solids, whose molar volumes are 100× to 1000× smaller. For condensed phases, use density (g/cm³) and molar mass: Vₘ = M / ρ. Water at 4 °C: 18.015 / 1.000 = 18.015 cm³/mol.

How do real gases deviate from ideal?

Van der Waals corrected the ideal law: (P + a(n/V)²)(V/n - b) = RT, where a corrects for attraction and b for finite molecular size. At 1 atm and room T, deviations are typically <1% for N₂, O₂, He; 2-3% for CO₂; 5-10% for water vapour. At high pressure or low temperature deviations swell.

What is the molar volume of air at sea level?

Treating air as ideal at 15 °C, 101.325 kPa: Vₘ = 8.314 × 288.15 / 101325 = 23.645 L/mol. A breath of 0.5 L at sea level contains 0.5/23.645 = 0.0212 mol of mixed gas - approximately 1.27 × 10²² molecules per inhalation, of which ~20% (0.25 × 10²²) is oxygen.

How do I convert mL of gas to moles?

First convert mL to L (÷ 1000), then divide by Vₘ at your conditions. Example: 250 mL of CO₂ at STP = 0.250 / 22.414 = 0.01115 mol = 0.491 g of CO₂. Half a litre of a typical respiratory CO₂ exhalation is ~0.022 mol, but biological respiration mixes air components.

Why is molar volume the same for all gases?

Avogadro's hypothesis (1811): equal volumes of gases at the same T and P contain the same number of molecules - true for ideal behaviour. Mass differs (H₂ at 2 g/mol vs O₂ at 32 g/mol) but the moles per volume is identical at given T, P. This is what made Cannizzaro's 1860 atomic-weight rescue possible.

What is NTP and when do I use it?

NTP (Normal Temperature and Pressure) is 20 °C, 1 atm - used by ISO and many industrial gas suppliers. Vₘ at NTP = 24.055 L/mol. Compressed-gas cylinders quoted in "Nm³" (normal cubic metres) are stated at NTP - critical for billing, safety calculations, and ASTM E681 flammability testing.

How do I include altitude correction?

Atmospheric pressure drops ~12% per 1000 m altitude. At 2000 m (Denver, La Paz partial): P ≈ 0.80 atm. The volume of a fixed mole of gas grows by 1/0.80 = 1.25× compared to sea level. Used for hot-air-balloon, aircraft, and high-altitude lab corrections.

Does humidity affect molar volume?

Yes - water vapour displaces dry air in the mixture, lowering the partial pressure of the other components. At 25 °C and 100% RH the partial pressure of water vapour is ~3.17 kPa - subtract from total to get dry-gas partial pressure. The IUPAC Gold Book gives reduction formulae for analytical chemists.

Ideal gas law · STP / NTP toggle · 5 preset conditions

Liters to Moles Calculator (Gas)

To convert litres of gas to moles, divide by 22.414 (the molar volume at STP) or use the full ideal gas law n = PV / RT for arbitrary T and P. This calculator handles both with a live inflating balloon and pressure / temperature gauges.

Law

PV = nRT

STP Vₘ

22.414 L/mol

0.082057

Presets

5 conditions

Quick Conversion

FROM (L)

TO (mol)1.00001

T (K)P (atm)

Formula: mol = P·V / (R·T)

Inflating Gas Balloon

Volume V (L)T (K)P (atm)

Moles n

1.0000

Vₘ (L/mol)

22.4139

T (°C)

0.00

P (kPa)

101.33

What this answer really means

At T = 273.15 K and P = 1.000 atm, one mole of ideal gas occupies 22.414 L. Your sample of 22.414 L therefore contains 1.0000 mol = 6.02e+23 molecules. Switch the temperature to body temperature (310 K) and the same balloon shrinks to 0.8807 mol.

Reference conditions

Conversion table at STP (0 °C, 1 atm)

Volume (L)	Moles (mol)	Molecules
0.001	0.000045	2.687e+19
0.01	0.000446	2.687e+20
0.1	0.004461	2.687e+21
1	0.044615	2.687e+22
2.24	0.099938	6.018e+22
5	0.223075	1.343e+23
10	0.446150	2.687e+23
22.414	1.000000	6.022e+23
50	2.230749	1.343e+24
100	4.461497	2.687e+24
250	11.153743	6.717e+24
1000	44.614973	2.687e+25
5000	223.074864	1.343e+26

Need to go the other way? Use the molarity tool for solutions

Formula

PV = nRT → n = PV / (RT)R = 0.082057 L·atm·mol⁻¹·K⁻¹ = 8.314 J·mol⁻¹·K⁻¹

Worked example: 5.0 L of O₂ at 25 °C (298.15 K) and 0.95 atm → n = (0.95 × 5.0) / (0.082057 × 298.15) = 0.1942 mol = 6.21 g of O₂.

How to convert L of gas to moles in 5 steps

Identify your conditions. STP, NTP, body temperature, or arbitrary lab values - pick a preset or enter T and P manually.
Enter the gas volume. Cylinder volumes are usually in m³ - multiply by 1000 to get litres.
Apply n = PV / RT. The balloon widget's LCD updates instantly; check pressure and temperature gauges visually.
Cross-check Vₘ. The molar volume readout (Vₘ = RT/P) shows what one mole occupies at your conditions - sanity check against 22.4 L/mol at STP.
Save the snapshot. Press Save to log the conversion (up to 20 entries) for downstream reporting.

From Boyle's tube to NIST's gas standards

Why this calculator exists: In 2026, an EPA Region 4 air-quality scientist preparing a Title V emissions report must convert stack-gas Nm³ measurements to mass flow for SO₂ and NOₓ. The IUPAC STP / NTP toggle and the live ideal-gas-law widget replace a spreadsheet + reference-card combo with one screen.

The story of the ideal gas law unfolded across two centuries. Robert Boyle reported in 1662 that for a fixed mass of gas at constant temperature, PV is constant - the first quantitative gas law. Jacques Charles noted in 1787 (published by Gay-Lussac 1802) that volume scales with absolute temperature at constant pressure. Joseph Louis Gay-Lussac in 1809 found that pressure scales with temperature at constant volume. Amedeo Avogadro in 1811 supplied the missing piece - equal volumes contain equal numbers of molecules - and Benoît Clapeyron unified the four laws in 1834 as PV = nRT.

The molar volume of 22.414 L/mol at 0 °C and 1 atm is the most-quoted constant in introductory chemistry. It comes from plugging R = 0.082057 L·atm/(mol·K) and T = 273.15 K and P = 1 atm into Vₘ = RT/P. The number predates the 2019 SI redefinition and was used unchanged by Cannizzaro at the 1860 Karlsruhe Congress to disentangle atomic from molecular weights - the same congress that gave Mendeleev (1869) the data he needed to build the periodic table.

Rutherford's 1911 nuclear model showed why ideal gases work: the volume of an atom's nucleus is ~10⁻¹⁵ of the atomic radius, so most of a low-density gas is empty space, justifying the "point particle" assumption. Real-gas corrections - van der Waals (1873) for finite size and attraction; virial coefficients (Onnes 1901) for higher-order effects - are needed only at high P or low T. For benchtop chemistry the ideal law is accurate to better than 1%.

IUPAC standardised the STP definition twice. The 1982 version (0 °C, 1 atm, Vₘ = 22.414 L/mol) remained the textbook standard until IUPAC's 1997 update changed the reference pressure to 100 kPa (Vₘ = 22.711 L/mol). Both are in use today - this calculator supports both as named presets. The BIPM 2019 SI redefinition fixed the kelvin via Boltzmann's constant and the second via the Cs-133 transition, ensuring R itself has zero uncertainty in its defined form: R = N_A × k_B = 8.31446261815... J/(mol·K) exactly.

NIST and ISO maintain gas-property reference data that this calculator's constants are traceable to. The CODATA 2018 release locked R, k_B, and N_A to their post-2019 defined values, and gas-cylinder regulators worldwide now bill in "normal cubic metres" (Nm³, at NTP) or "standard cubic metres" (Sm³, at STP) with these constants embedded in the tariff math. Linde, Air Liquide, Praxair, and Air Products all publish public conversion factors traceable to the same metrological chain.

This tool implements PV = nRT in five-line clarity with a live balloon visual and a five-condition preset set. For solutions see molarity; for combining gas moles with mass see molar mass.

Liters ↔ moles (ideal gas) - frequently asked questions

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“I teach a lecture on tropospheric chemistry and use the live balloon widget to show that 1 mol of CO₂ occupies 22.4 L at STP - exactly. Students never forget the visual.”

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Mr. Cassius Owens

EPA Region 4 air-quality scientist

May 8, 2026

“Argentina's national curriculum uses 22.4 L/mol but my AP students see 22.711 in IUPAC sources. The dual-STP preset settles the debate every September.”

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February 12, 2026

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