Liters per Minute to CFH: Flow Conversion

This calculator converts a flow rate from liters per minute (L/min) to cubic feet per hour (cfh or ft³/h). You enter the flow rate in L/min, and it returns the equivalent in cfh, along with the result in cubic feet per minute for reference. The conversion uses the standard relationship between liters and cubic feet and between minutes and hours.

Formula

The conversion is a two-step unit change:

• 1 liter = 0.035314666721489 cubic feet (exactly 1 L = 0.001 m³ and 1 ft³ = 0.028316846592 m³)
• 1 hour = 60 minutes

So the formula is:

cfh = L/min × 60 × 0.035314666721489

Which simplifies to:

cfh = L/min × 2.11888000328934

Where:

• L/min = flow rate in liters per minute
• cfh = flow rate in cubic feet per hour

If you need the intermediate cubic feet per minute (cfm), divide the L/min value by 28.316846592 (the number of liters in one cubic foot).

Worked Example

Using the default value of 100 L/min:

1. Convert liters to cubic feet: 100 L × 0.035314666721489 = 3.5314666721489 ft³
2. Convert minutes to hours: multiply by 60 → 3.5314666721489 × 60 = 211.888000328934 cfh
3. Round to two decimals: 211.89 cfh

The calculator gives 211.89 cfh, matching the manual calculation.

When to Use This Conversion

You will need L/min to cfh conversion in several practical situations:

• HVAC and ventilation: Many blower and fan specifications list airflow in CFM or CFH, while some flow meters and rotameters read in L/min.
• Compressed air systems: Compressor output is often quoted in CFM, but the flow sensor on a pneumatic line may display L/min.
• Gas appliances and combustion: Burner gas flow or orifice sizing may use CFH, while test instruments report L/min.
• Aquarium and pond pumps: Pump ratings vary by manufacturer; converting lets you compare pumps from different regions.
• Laboratory and medical gas flow: Regulators often show L/min, but facility design documents use CFH.

Always check which unit the equipment manual actually uses. Many devices have both scales, but if only one is present, this conversion fills the gap.

How to Read the Result

The result is a volumetric flow rate at the actual pressure and temperature of the gas or liquid. For liquids, the conversion is exact because liters and cubic feet are fixed volume units. For gases, the volume changes with pressure and temperature, so the conversion only holds if both the L/min reading and the CFH target are at the same conditions. If the gas is at standard conditions (often 20°C and 1 atm), the conversion is still the same factor, but the actual volume at other conditions will differ.

A quick mental check: 1 L/min is about 2.12 cfh. So 10 L/min ≈ 21.2 cfh, 50 L/min ≈ 106 cfh, and 100 L/min ≈ 212 cfh. If you are working with a small rotameter reading 5 L/min, that is roughly 10.6 cfh.

Common Mistakes and Unit Mix-Ups

• Confusing CFH with CFM: CFH is per hour, CFM is per minute. A common error is to multiply by 60 when converting CFM to CFH (correct) but then forget that the L/min value already has a per-minute component. The factor 2.11888 already includes the 60.
• Using the wrong liter-to-cubic-foot factor: Some sources round to 0.0353, which is fine for rough work, but for accurate engineering, use the exact value 0.035314666721489.
• Swapping gallons and liters: A US gallon is 3.78541 liters, not 1. If you have a flow in gallons per minute (GPM), you must first convert to liters, then to cfh. The factor for GPM to cfh is 8.02083, not 2.11888.
• Forgetting to round consistently: If you round intermediate steps too early, the final answer can drift. Keep full precision until the end.

Practical Examples with Common Flow Rates

• 2 L/min (typical oxygen concentrator): 2 × 2.11888 = 4.24 cfh
• 15 L/min (small compressor): 15 × 2.11888 = 31.78 cfh
• 250 L/min (industrial blower): 250 × 2.11888 = 529.72 cfh
• 1000 L/min (large fan): 1000 × 2.11888 = 2118.88 cfh

These examples show the linear relationship: double the L/min, double the cfh.

Limits of the Conversion

This conversion is purely dimensional – it does not account for fluid properties. For liquids, it is exact. For gases, the actual volumetric flow depends on pressure and temperature. If you are working with a gas at high pressure (e.g., 10 bar), the L/min reading from a mass flow meter may already be normalized to standard conditions, but a rotameter reading will be at line conditions. In that case, the conversion factor is still 2.11888, but you must ensure both the input and the desired output are at the same reference conditions. If they are not, you need additional pressure and temperature corrections (Boyle’s law and Charles’s law).

Also, the conversion does not apply to mass flow rates (kg/h or lb/h). To convert mass flow to volumetric flow, you need the fluid density at the operating conditions.

Frequently Asked Questions

Is 1 L/min equal to 2.11888 CFH exactly?

Yes, because 1 liter is exactly 0.035314666721489 cubic feet, and there are 60 minutes in an hour. Multiplying 0.035314666721489 by 60 gives 2.11888000328934. That is the exact conversion factor, though many people round to 2.12 for quick estimates.

What is the difference between CFH and CFM?

CFH is cubic feet per hour, CFM is cubic feet per minute. Since there are 60 minutes in an hour, 1 CFM equals 60 CFH. The L/min to CFH conversion already accounts for the minute-to-hour step, so you do not multiply by 60 again.

How do I convert CFH back to L/min?

Divide the CFH value by 2.11888. For example, 100 CFH ÷ 2.11888 = 47.19 L/min. This is the inverse of the calculator’s formula.

Does this conversion work for water flow?

Yes, for any liquid or gas, as long as you are measuring volumetric flow. The conversion factor depends only on the units, not on what fluid is flowing. However, if you need mass flow (kg/h), you must multiply by the fluid density.

Why do some compressor specs use CFM and others use L/min?

Manufacturers in different regions use the local customary unit. US-based companies often use CFM, while European and Asian companies use L/min or m³/h. The conversion lets you compare equipment from different sources.

What if my flow meter shows standard liters per minute (SLM) instead of L/min?

SLM is liters per minute at standard conditions (usually 0°C and 1 atm, or 20°C and 1 atm depending on the standard). The conversion factor is still 2.11888, but the actual volume at your operating conditions may differ. Always check the reference conditions of your meter.

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in lpm | Flow rate | L/min | 100 | 0
out cfh | Flow rate | cfh | lpm * 2.1188800032893 | 2
out cfm | Flow rate | cfm | lpm / 28.316846592 | 2