Cubic Feet to Liters per Minute: Conversion
- Flow rate
- L/s
- Result
- Flow rate
- 100 ft³/min
- You entered
This calculator converts a flow rate from cubic feet per minute (CFM) to liters per minute (L/min). You enter the value in cubic feet per minute, and it returns the equivalent flow rate in liters per minute, along with the same value expressed in liters per second for quick reference.
Formula
The conversion relies on the exact relationship between the cubic foot and the liter. One cubic foot is defined as exactly 28.316846592 liters. Therefore, to convert a flow rate from cubic feet per minute to liters per minute, you multiply by this factor:
L/min = ft³/min × 28.316846592
Where:
- ft³/min (CFM) is the volumetric flow rate in cubic feet per minute.
- L/min is the volumetric flow rate in liters per minute.
- 28.316846592 is the exact number of liters in one cubic foot.
If you need liters per second instead, divide the result by 60, because there are 60 seconds in a minute.
Worked Example
Using the default value of 100 ft³/min from the calculator:
- Start with the flow rate: 100 ft³/min.
- Multiply by the conversion factor: 100 × 28.316846592 = 2831.6846592 L/min.
- Round to two decimal places: 2831.68 L/min.
The calculator shows 2831.68 L/min, which matches. For liters per second, divide that by 60: 2831.6846592 ÷ 60 = 47.19474432 L/s, rounded to three decimals as 47.195 L/s.
Why Convert Between CFM and L/min?
Cubic feet per minute is the standard flow unit in the United States and in many HVAC, air compressor, and industrial applications. Liters per minute is common in most other countries and in medical, laboratory, and automotive contexts. If you are comparing equipment from different regions or working with international specifications, you will often need to switch between the two. For example, a vacuum cleaner rated at 100 CFM might be listed as 2831.68 L/min in a European catalog. Understanding the conversion helps you compare performance directly without guesswork.
Common Applications and Real-World Context
- HVAC systems: Air handling units and ductwork are rated in CFM in the US, but many international standards use L/s or L/min.
- Air compressors: The free air delivery (FAD) of a compressor is often quoted in CFM in the US and in L/min in Europe.
- Vacuum cleaners and dust collectors: Suction strength is often given in CFM or L/min depending on the market.
- Medical oxygen concentrators: Flow rates are typically expressed in L/min, so a device designed for the US market may need conversion for international use.
- Aquarium and hydroponic pumps: Pump output may be listed in either unit, so conversion is needed for sizing.
How to Read the Result
The result tells you the same volumetric flow rate in a different unit. A higher number in L/min simply reflects that liters are smaller than cubic feet. For example, 1 ft³/min equals 28.316846592 L/min, so the numeric value always increases when converting from CFM to L/min. When comparing two devices, always ensure both flow rates are in the same unit before judging which is larger.
Common Mistakes and How to Avoid Them
- Using the wrong conversion factor: Some sources round to 28.32, which is fine for rough estimates but can cause errors in precise work. Use 28.316846592 for exact conversions.
- Confusing CFM with other flow units: Do not mix up cubic feet per minute with cubic feet per second or gallons per minute. Each requires a different factor.
- Forgetting to convert time units: If you start with a flow rate in cubic feet per second, you must multiply by 60 to get per minute before applying the liter conversion.
- Rounding too early: Round only the final answer, not intermediate steps, to avoid accumulating errors.
Limitations of the Conversion
This conversion is purely mathematical and assumes the same fluid and the same conditions on both sides. It does not account for temperature, pressure, or fluid density, which can affect actual volumetric flow in real systems. For gases, the volume changes with temperature and pressure, so a CFM rating at one condition may not equal the same L/min rating at another condition. Always check the reference conditions (e.g., standard temperature and pressure) when comparing flow rates for gases. For liquids, the conversion is straightforward because liquids are nearly incompressible.
Frequently Asked Questions
How many liters per minute is 1 CFM?
Exactly 28.316846592 liters per minute. So if you have 1 ft³/min, you have 28.32 L/min when rounded to two decimals.
Can I convert L/min back to CFM?
Yes, divide the L/min value by 28.316846592. For example, 100 L/min ÷ 28.316846592 = 3.53 ft³/min.
Why is the CFM to L/min conversion factor not a round number?
Because the foot and the liter are defined independently. The foot is defined as 0.3048 meters exactly, and the liter is defined as one cubic decimeter (0.001 m³). Cubing 0.3048 gives 0.028316846592 m³, which equals 28.316846592 liters.
Is CFM the same as cubic feet per second?
No. CFM is per minute, while cubic feet per second (cfs) is per second. To convert cfs to CFM, multiply by 60. To convert cfs to L/min, multiply by 60 × 28.316846592 = 1699.01079552.
What is the difference between CFM and SCFM?
CFM is simply the volumetric flow rate at the actual conditions. SCFM (standard cubic feet per minute) is the flow rate corrected to a standard temperature and pressure (usually 60°F and 14.7 psi). This conversion does not apply to SCFM because it involves gas law corrections.