Molar Flow Rate Converter
Convert a molar flow rate between mol/s, mmol/s, mol/min, mol/h, kmol/h, and mol/day. Enter a value, then select the starting and target units.
Convert Molar Flow Rate Between Units
Molar Flow Rate Formula
Where:
- \(q_{\mathrm{in}}\) — the entered molar flow rate in the selected starting unit
- \(q_{\mathrm{out}}\) — the converted molar flow rate in the selected target unit
- \(f_{\mathrm{from}}\) and \(f_{\mathrm{to}}\) — the numbers of mol/s represented by one starting unit and one target unit, respectively
The formula first expresses the entered rate in mol/s, then divides by the mol/s equivalent of the target unit. It changes the unit, not the physical flow rate.
Molar Flow Rate – Calculation Example
Example: Convert the calculator’s default value of 2 mol/s to mol/h.
One mol/h equals \(1/3600\) mol/s, so:
\[ q_{\mathrm{out}}=2\,\frac{\mathrm{mol}}{\mathrm{s}}\times\frac{3600\,\mathrm{s}}{1\,\mathrm{h}}=7200\,\frac{\mathrm{mol}}{\mathrm{h}} \]
Result: 2 mol/s = 7,200 mol/h.
How to use the calculator
- Enter a nonnegative number in Molar flow rate value. The default is 2.
- Choose the unit of that number in From unit. The default is mol/s.
- Choose the unit you need in To unit. The default is mol/h.
- Read Converted Molar Flow Rate. The result is labeled with the selected target unit.
You can select the same unit in both menus to leave the number unchanged. To reverse a conversion, swap the selections in From unit and To unit, then enter the value you want to convert back.
What molar flow rate means
Molar flow rate is the amount of a substance passing a point or entering or leaving a system per unit time. Amount of substance is measured in moles. For example, 2 mol/s means that 2 moles pass the chosen point each second. The unit conversion does not depend on which chemical is flowing: one mole is the same amount-of-substance unit whether it describes water, oxygen, or another material.
Molar flow rates are useful in reactor feed calculations, material balances, and stoichiometry. If a process receives two streams measured in different units, convert them to a common unit before adding or comparing their rates. A rate in mol/day may be convenient for reporting daily production, while mol/s may be more useful for a calculation expressed in seconds. Neither unit indicates a different physical flow; only the numerical representation changes.
Molar flow rate differs from mass flow rate, which measures mass per unit time. Converting between the two requires the substance’s molar mass as well as its flow rate. If you are working with kilograms per second or pounds per hour, use the Mass Flow Rate Converter for conversions between mass-flow units; changing a molar-flow unit alone will not produce a mass-flow value.
Supported units and conversion factors
The calculator uses mol/s as its reference unit. Each factor below tells you how many mol/s equal one unit in the left column. For example, 1 kmol/h is \(1000/3600\) mol/s because a kilomole contains 1,000 moles and an hour contains 3,600 seconds.
| Unit | Equivalent in mol/s |
|---|---|
| mol/s | 1 |
| mmol/s | 0.001 |
| mol/min | 1/60 |
| mol/h | 1/3600 |
| kmol/h | 1000/3600 |
| mol/day | 1/86400 |
To check a conversion by hand, multiply the entered number by its starting-unit factor and divide by its target-unit factor. For instance, converting from mol/h to kmol/h divides the numerical value by 1,000. Converting from mol/day to mol/h divides it by 24. These relationships follow from the unit prefixes and time intervals, without requiring any information about the material.
Assumptions and practical tips
The time conversions assume a day of exactly 24 hours, an hour of 60 minutes, and a minute of 60 seconds. The converter accepts zero and positive values. It reports the converted number rounded for display, so a very small nonzero result may appear as zero; choose a smaller unit, such as mmol/s, when you need a more readable number.
Check that the original measurement is an amount-of-substance flow rate before entering it. A volumetric gas flow rate cannot be converted to mol/s from its units alone: temperature, pressure, and other conditions may be needed to determine the amount of gas. For related gas calculations, see the Pressure Converter. If your work concerns dissolved-gas equilibrium rather than flow, the Henry’s Law Calculator addresses a different relationship.
Frequently Asked Questions
What is a normal molar flow rate?
There is no universal normal value. A suitable molar flow rate depends on the process, equipment size, and substance being handled. Compare a measured rate with the design specification or an expected range for that particular system. A large number in mol/day may describe the same flow as a much smaller number in mol/s.
How do I convert mmol/s to kmol/h by hand?
Multiply by 0.0036. One millimole is \(10^{-6}\) kilomoles, and one hour has 3,600 seconds, so the combined multiplier is \(10^{-6}\times3600=0.0036\). For example, \(500\,\mathrm{mmol/s}=500\times0.0036=1.8\,\mathrm{kmol/h}\). Check both the amount prefix and the time unit; changing only one gives the wrong result.
How can I calculate molar flow rate from concentration and volumetric flow rate?
Multiply concentration by volumetric flow rate, provided their volume units match: \(\dot n=c\dot V\). For example, a solution at \(0.2\,\mathrm{mol/L}\) flowing at \(3\,\mathrm{L/min}\) carries \(0.6\,\mathrm{mol/min}\) of the specified solute. Use the concentration of the substance whose molar flow you want, not the total concentration of every component.
How do I calculate mass flow rate from molar flow rate?
Multiply by the substance’s molar mass: \(\dot m=\dot nM\). For water, \(0.5\,\mathrm{mol/s}\times18.015\,\mathrm{g/mol}\approx9.01\,\mathrm{g/s}\). For a mixture, calculate each component’s mass flow using its own molar mass, then add them. A unit conversion between molar flow units alone cannot supply the missing molar-mass information.
Can I convert a gas flow in L/min directly to mol/s?
Not from the volume rate alone. For a gas that can be treated as ideal, use \(\dot n=P\dot V/(RT)\), with absolute pressure, absolute temperature, and consistent units for the gas constant. Confirm whether the stated volume rate refers to actual or standard conditions. Gas composition and non-ideal behavior can also matter, especially at high pressures.
What does a negative molar flow rate mean?
A negative value usually indicates flow opposite to a chosen positive direction, not a negative quantity of substance. This converter accepts nonnegative values, so convert the magnitude and retain the minus sign separately if your calculation uses signed flows. State your direction convention when reporting inlet and outlet rates in a material balance.
Is molar flow rate the same as molar flux?
No. Molar flow rate is an amount per time, such as mol/s; molar flux is an amount per area per time, such as mol/(m²·s). If flux is uniform and perpendicular to an area, multiply it by that area to obtain molar flow rate: \(\dot n=JA\). If flux varies across the area, it must be integrated instead.
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