To convert an air flow, remember one base: 1 m³/min = 1,000 l/min = 60 m³/h ≈ 35.3 cfm, and 1 cfm ≈ 28.3 l/min. These are standard unit conversions. They are enough to compare a data sheet in l/min with a tool manual in cfm, provided you check two more things: the pressure at which the flow is stated, and the type of flow measured.
Our flow and pressure converter does the arithmetic for you. This guide explains what lies behind it.
Flow units and their equivalents
| Unit | Where you find it | In l/min |
|---|---|---|
| l/min | Metric data sheets, tool manuals | 1 |
| l/s | Some industrial data sheets | 60 |
| m³/min | Screw compressor data sheets | 1,000 |
| m³/h | Dryers, filters, pipework | 16.67 |
| cfm (cubic feet per minute) | Tools and data sheets in imperial units | 28.317 |
To go from one unit to another, convert to l/min first, then to the target unit:
- cfm to l/min: multiply by 28.3.
- l/min to cfm: divide by 28.3.
- m³/min to m³/h: multiply by 60.
- m³/h to l/min: multiply by 1,000, then divide by 60.
A step-by-step example
An orbital sander states 12 cfm at 90 psi in its manual, a typical order of magnitude for this tool, used here as an indication. It is added to a workshop that already uses 0.9 m³/min. What is the total?
- Sander: 12 × 28.3 ≈ 340 l/min.
- Existing workshop: 0.9 m³/min × 1,000 = 900 l/min.
- Total: 340 + 900 = 1,240 l/min, or about 1.24 m³/min, 74 m³/h or 44 cfm.
You then compare this total with a compressor's flow, in the same unit and at the same pressure. Each tool's consumption is the figure in its manual: example values never replace manufacturer data.
Trap 1: a flow without a pressure means nothing
A compressor delivers less air as pressure rises. The data sheet of the S 110 gives 1.7 m³/min at 8 bar, 1.4 m³/min at 10 bar and 1.1 m³/min at 13 bar. Comparing one machine's flow at 7 bar with another's at 10 bar compares two different things. Always bring both data sheets to the same pressure.
On the tool side, the reference pressure is often 90 psi, about 6.2 bar: the working pressure of most air tools.
Trap 2: intake flow or delivered flow
A data sheet may give the intake flow (or the displacement of a piston compressor), which measures the air going in, or the delivered flow, known as FAD (free air delivery), which measures the air actually available at the outlet according to ISO 1217. The second is always lower. The flows on AIRSTAHL data sheets are delivered flows. For the other lines of a data sheet, see reading a compressor data sheet.
Trap 3: free air, normal and compressed cubic metres
A cubic metre is not always the same:
- A cubic metre of free air, as in FAD, refers to intake conditions: around 1 bar and 20 °C in the ISO 1217 reference conditions.
- A normal cubic metre (Nm³) refers to 0 °C and 1.013 bar. The air is denser: 1 Nm³ equals about 1.09 m³ of free air at ISO 1217 conditions. Dryers, filters and flow meters are often rated in Nm³/h. A gap of 8 to 9% matters when you size tightly.
- A cubic metre of compressed air is a volume under pressure. At 8 barg, it holds about 9 m³ of free air. A flow stated as a compressed volume cannot be compared with a FAD figure.
Likewise, scfm is cfm brought to standard conditions, which vary between sources: check them before comparing.
And kW?
There is no exact conversion between flow and power, because a motor's flow depends on pressure. To estimate the power that matches a flow in cfm, the CFM and kW configurator uses the real flows of our compressors, read from their data sheets, at the pressure you choose.
Our range in every unit
Delivered flows of the S series, from the data sheets, converted with the equivalents above:
| Model | Data sheet flow | l/min | m³/h | cfm |
|---|---|---|---|---|
| S 55, 5.5 kW | 0.6 m³/min at 8 bar | 600 | 36 | 21 |
| S 75, 7.5 kW | 1.1 m³/min at 8 bar | 1,100 | 66 | 39 |
| S 110, 11 kW | 1.7 m³/min at 8 bar | 1,700 | 102 | 60 |
| S 150, 15 kW | 2.2 m³/min at 8 bar | 2,200 | 132 | 78 |
| S 220 PM, 22 kW | 3.2 m³/min at 10 bar | 3,200 | 192 | 113 |
In the sander example, the 1,240 l/min requirement exceeds the S 75 (1,100 l/min at 8 bar). The S 110 covers it, with the margin that sound sizing calls for. For the full method, listing tools and estimating simultaneous use, read what size compressor do I need.
Key points
- Convert everything to l/min before adding up.
- Compare two flows at the same pressure and of the same type (FAD against FAD).
- Watch out for Nm³ and compressed volumes.
The configurator adds up your tools' consumption and suggests a model. For a more complex case, send us your tool list in a quote request.