CFM to CMH converter
Convert airflow between m³/h (CMH), m³/min (CMM), CFM, L/s and m³/s, for moving between drawings, US equipment schedules and SI equations.
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Airflow unit definitions
- CMH (m³/h)
- Cubic metres per hour. The usual unit on Korean drawings, schedules and duct sizing.
- CMM (m³/min)
- Cubic metres per minute = m³/h ÷ 60. Common on fan performance tables.
- CFM (ft³/min)
- Cubic feet per minute. With 1 ft = 0.3048 m, 1 ft³ = 0.0283168 m³ and 1 CFM = 1.69901 m³/h. Used in US catalogues.
- L/s
- Litres per second = m³/h ÷ 3.6. Used by ASHRAE 62.1 outdoor air rates (L/s per person) and European data.
- m³/s
- Cubic metres per second = m³/h ÷ 3,600. The form to put into SI equations such as velocity = flow ÷ area.
Rules of thumb and examples
Mental shortcut: CFM ≈ m³/h × 0.6 and m³/h ≈ CFM × 1.7 (exactly 0.5886 and 1.699). 2,000 CFM is about 3,400 m³/h.
Duct velocity: 1,000 m³/h = 0.2778 m³/s through a 300 mm round duct (0.0707 m²) gives 0.2778 ÷ 0.0707 = 3.93 m/s.
Air changes: 1,000 m³/h into a 100 m² office with a 2.7 m ceiling (270 m³) is 1,000 ÷ 270 = 3.7 air changes per hour.
m³/h to CFM, m³/min, L/s and m³/s
Common airflows to four significant digits, with the same factors as the converter above.
| CMH m³/h | CFM ft³/min | CMM m³/min | L/s | m³/s |
|---|---|---|---|---|
| 100 | 58.86 | 1.667 | 27.78 | 0.02778 |
| 200 | 117.7 | 3.333 | 55.56 | 0.05556 |
| 300 | 176.6 | 5 | 83.33 | 0.08333 |
| 500 | 294.3 | 8.333 | 138.9 | 0.1389 |
| 800 | 470.9 | 13.33 | 222.2 | 0.2222 |
| 1,000 | 588.6 | 16.67 | 277.8 | 0.2778 |
| 1,500 | 882.9 | 25 | 416.7 | 0.4167 |
| 2,000 | 1,177 | 33.33 | 555.6 | 0.5556 |
| 3,000 | 1,766 | 50 | 833.3 | 0.8333 |
| 5,000 | 2,943 | 83.33 | 1,389 | 1.389 |
| 8,000 | 4,709 | 133.3 | 2,222 | 2.222 |
| 10,000 | 5,886 | 166.7 | 2,778 | 2.778 |
| 15,000 | 8,829 | 250 | 4,167 | 4.167 |
| 20,000 | 11,770 | 333.3 | 5,556 | 5.556 |
| 30,000 | 17,660 | 500 | 8,333 | 8.333 |
| 50,000 | 29,430 | 833.3 | 13,890 | 13.89 |
| 100,000 | 58,860 | 1,667 | 27,780 | 27.78 |
CFM to m³/h table
For reading US equipment schedules in SI units.
| CFM ft³/min | CMH m³/h | CMM m³/min | L/s |
|---|---|---|---|
| 50 | 84.95 | 1.416 | 23.6 |
| 100 | 169.9 | 2.832 | 47.19 |
| 200 | 339.8 | 5.663 | 94.39 |
| 400 | 679.6 | 11.33 | 188.8 |
| 500 | 849.5 | 14.16 | 236 |
| 1,000 | 1,699 | 28.32 | 471.9 |
| 2,000 | 3,398 | 56.63 | 943.9 |
| 3,000 | 5,097 | 84.95 | 1,416 |
| 5,000 | 8,495 | 141.6 | 2,360 |
| 10,000 | 16,990 | 283.2 | 4,719 |
| 20,000 | 33,980 | 566.3 | 9,439 |
| 50,000 | 84,950 | 1,416 | 23,600 |
Sources
- NIST Special Publication 811 (2008), Appendix B: 1 ft³ = 0.028316846592 m³
- International yard and pound agreement, 1959 (1 ft = 0.3048 m)
- ASHRAE Standard 62.1 (outdoor air rates in L/s)
Frequently asked questions
What is a quick way to estimate m³/h from CFM?
Multiply CFM by 1.7 (exactly 1.699). The other way, multiply m³/h by 0.6 (exactly 0.5886). 1,000 m³/h = 588.6 CFM.
How do m³/min (CMM) and m³/h (CMH) differ?
Only the time base: m³/h = m³/min × 60, so a 100 m³/min fan moves 6,000 m³/h.
Do SCFM and ACFM convert with the same factor?
The volume factor is the same, but the reference state differs: SCFM is airflow at standard conditions, ACFM at the actual temperature and pressure. When temperature or altitude differ a lot, compare mass flow (kg/h) using the specific volume from the psychrometric calculator.
Last updated 2026-10-12.