Home›Converters›Science›Molar Flow Converter

Molar Flow Converter

Science

Convert molar flow rate between moles per second, moles per hour, kilomoles per hour, and pound-moles per hour — used for chemical engineering.

Reviewed by the thecalcu.com team · Last updated July 8, 2026

From
To
All conversionsfor 1 Moles per Hour (mol/hr)
Moles per Second (mol/s)0.000277778
Moles per Minute (mol/min)0.016666647
Moles per Hour (mol/hr)1
Kilomoles per Hour (kmol/hr)0.001
Pound-Moles per Hour (lb-mol/hr)0.0022046223

What is a Molar Flow?

The Molar Flow Converter converts molar flow rate between moles per second, moles per minute, moles per hour, kilomoles per hour, and the US customary pound-moles per hour. Molar flow rate measures how many moles of a substance pass a point per unit time, the natural unit for chemical reaction calculations, since reactions proceed according to molar stoichiometric ratios rather than mass ratios.

Enter a value in any supported unit and the converter calculates the equivalent instantly. For the related mass-based quantity, see the Mass Flow Converter.

Why Use a Molar Flow Converter?

Process flow diagrams and reactor design calculations report molar flow rate in whatever unit convention matches the plant's scale and region, mol/s for small or laboratory-scale processes, kmol/hr for typical industrial process streams, and lb-mol/hr in US-based chemical engineering practice. Comparing or combining these across a plant design or between equipment specifications requires accurate conversion.

Who Should Use This Converter?

  • Chemical and process engineers converting molar flow rate data across process flow diagrams and equipment specifications.
  • Reactor design engineers working through reaction rate and stoichiometry calculations that mix molar flow units.
  • Chemical engineering students learning to work with molar flow rate data across metric and US customary unit systems.
  • Petrochemical and refinery engineers working with mixed-unit process data from international equipment suppliers.

What Insights Does the Molar Flow Converter Give You?

The main output is the converted value in your chosen target unit, calculated precisely from the fixed multiplier relationship between units. Because molar flow rate spans a wide practical range depending on process scale, the converter helps confirm you're comparing values consistently across a plant design or calculation.

How to use this Molar Flow calculator

  1. Choose your starting unit from the source dropdown, for example, "Moles per Hour (mol/hr)".
  2. Enter the numeric value you want to convert in the input field.
  3. Choose your target unit from the destination dropdown, for example, "Kilomoles per Hour (kmol/hr)".
  4. Read the converted result, which updates instantly as you type or change units.
  5. Use the swap (⇅) button if you need to reverse the conversion direction.
  6. Use the copy button to grab the result for a reactor design calculation or process flow diagram.
Show formula & methodology ↓Show less ↑

Formula & Methodology

The converter's base unit is moles per second (mol/s). Every supported unit has a fixed multiplier:

- 1 mole per minute (mol/min) = 0.016667 mol/s
- 1 mole per hour (mol/hr) = 0.000278 mol/s
- 1 kilomole per hour (kmol/hr) = 0.277778 mol/s
- 1 pound-mole per hour (lb-mol/hr) = 0.125998 mol/s

Any conversion follows:

Result = Input × (toBase of source unit ÷ toBase of target unit)

Worked example, converting 10 kmol/hr to mol/s:

Result = 10 × (0.277778 ÷ 1) = 2.778 mol/s

This is the value you'd use directly in an SI-unit reaction kinetics calculation.

Related Tools

You may also find these useful: Molar Concentration Converter, Flow Converter.

Frequently Asked Questions

What is molar flow rate?
Molar flow rate measures how many moles of a substance pass a given point per unit time, expressed in units like moles per second, commonly used in chemical engineering and reaction kinetics, where reaction rates and stoichiometry are naturally expressed in moles rather than mass.
How do I convert mol/hr to kmol/hr?
Divide the mol/hr value by 1,000, since one kilomole equals 1,000 moles. Enter your value with 'Moles per Hour (mol/hr)' as the source and 'Kilomoles per Hour (kmol/hr)' as the target to apply this automatically.
Why do chemical engineers prefer molar flow over mass flow for reaction calculations?
Chemical reactions proceed according to molar stoichiometric ratios (like 2 moles of hydrogen reacting with 1 mole of oxygen), not mass ratios, so expressing flow rates in moles makes reactor design and reaction rate calculations far more direct than converting through mass and molecular weight repeatedly.
How do I convert molar flow rate to mass flow rate?
Multiply the molar flow rate by the substance's molar mass (mass flow = molar flow × molar mass), see the [Mass Flow Converter](/mass-flow-converter/) for the resulting mass-based flow unit conversions.
What is a pound-mole, and why is it used in US chemical engineering?
A pound-mole (lb-mol) is the US customary equivalent of a mole, defined so that one lb-mol contains a mass in pounds numerically equal to the substance's molecular weight, just as one mole of a substance weighs its molecular weight in grams. It's used to keep US-based process calculations consistent with pound-based mass units.
What is a typical molar flow rate for an industrial chemical reactor?
This varies enormously by reactor scale and reaction type, laboratory-scale reactions might involve millimoles per second, while large industrial reactors can process kilomoles per hour or more, so context determines what's typical for a specific process.
How does molar flow relate to gas flow calculations?
For gases, molar flow rate relates directly to volumetric flow rate through the ideal gas law (PV = nRT), making molar flow a natural unit for gas process calculations where pressure and temperature significantly affect volume.
Why is kmol/hr a common unit in process engineering flow diagrams?
Kilomoles per hour keeps typical industrial process stream numbers in a convenient, readable range, expressing large-scale plant flows in mol/s would produce awkwardly large numbers, so kmol/hr is the conventional unit on most process flow diagrams and mass/mole balance sheets.
Can I convert molar flow rate directly between different substances?
The unit conversion itself (mol/s to kmol/hr, for example) works the same regardless of substance, but converting a molar flow rate to mass flow rate requires the specific substance's molar mass, which differs for every chemical compound.
What industries commonly use molar flow rate calculations?
Chemical processing, petrochemical refining, pharmaceutical manufacturing, and any industry involving chemical reactions or gas processing rely heavily on molar flow rate for reactor design, mass balance calculations, and process control.
Also known as
molar flow rate convertermol/s to kmol/hr converterlb-mol/hr converterchemical engineering flow convertermolar flow units