How do I convert volume flow to molar flow for gases?

Use the ideal gas law: n/t = PV/(RT). At STP (0°C, 1 atm), 1 mole occupies 22.4 L. So molar flow (mol/s) = volume flow (L/s) / 22.4. At other conditions, use PV = nRT with actual T and P.

Why is molar flow preferred for reactor design?

Stoichiometry works in moles: if 2A + B → C, you need 2 mol A per mol B. Using molar flow rates, you directly see if reactant ratios are correct. Mass or volume flow would require molecular weight conversions and density corrections at every step.

What is a pound-mole?

A pound-mole (lb-mol) contains Avogadro's number of molecules but uses pounds for mass: 1 lb-mol of CO₂ weighs 44 lb (not grams). It's 453.6 times larger than a gram-mole. Used in US engineering to keep mass units consistent with pounds.

Molar Flow Converter

About Molar Flow Rate Conversion

Molar flow rate measures the number of moles of substance passing a point per unit time—the most chemically meaningful way to express flow because chemical reactions occur in molar proportions. Unlike mass or volume flow, molar flow directly relates to stoichiometry: if a reaction requires two moles of reactant A per mole of B, molar flow rates immediately tell you whether reactant ratios are correct without any conversion calculations.

The SI unit is moles per second (mol/s), but kilomoles per hour (kmol/h) is the workhorse unit for industrial chemical processes where flows are substantial and hourly rates match production schedules. The pound-mole (lb-mol) remains common in US chemical industry. Molar flow is fundamental to reactor design (sizing, conversion calculations), material balances around process units, equilibrium and kinetics calculations, and process simulation software. When dealing with gas mixtures, molar flow also relates directly to volume through the ideal gas law at standard conditions.

Our converter handles all standard molar flow rate units for chemical engineering, process design, and laboratory applications.

Common Molar Flow Rate Conversions

From	To	Multiply By
mol/s	kmol/h	3.6
kmol/h	mol/s	0.2778
mol/s	mol/min	60
mol/min	mol/s	0.01667
kmol/h	lb-mol/h	2.205
lb-mol/h	kmol/h	0.4536
mol/s	mmol/s	1,000
kmol/day	mol/s	0.01157

Molar Flow Rate Unit Reference

Mole per second (mol/s) – The SI unit for molar flow rate. Directly compatible with reaction rate expressions (mol/s per volume = rate), kinetic calculations, and scientific literature. Used in research, laboratory settings, and theoretical calculations. 1 mol/s is a substantial flow rate—laboratory reactions often involve millimoles per second.

Kilomole per hour (kmol/h) – The standard industrial unit for chemical process engineering worldwide. Convenient for large-scale continuous processes where flows are substantial and hourly rates align with production reporting. 1 kmol/h = 0.2778 mol/s. Process flow diagrams, material balances, and simulation software (Aspen, HYSYS) typically use kmol/h as the default molar flow unit.

Pound-mole per hour (lb-mol/h) – US engineering unit used extensively in American chemical industry. 1 lb-mol = 453.6 mol (same ratio as pound to gram). Maintains unit consistency when other flows are in pounds and temperatures in Rankine/Fahrenheit. Many US process simulators and equipment specifications use lb-mol/h. 1 lb-mol/h ≈ 0.126 mol/s.

Mole per minute (mol/min) – Intermediate unit convenient for laboratory-scale continuous processes and some analytical methods. 1 mol/min = 60 mol/h. Used in flow chemistry, gas chromatography calibrations, and bench-scale reactor studies where second-based rates are too fine and hourly rates too coarse.

Standard volume flow (Sm³/h, SCFH) – For ideal gases at standard conditions, molar flow relates to volume flow by n = PV/RT. At STP (0°C, 1 atm), 1 kmol occupies 22.4 m³. This relationship allows conversion between molar and volumetric flow for gases when standard conditions are specified.