SettingsSettings for this calculationUS
The airflow in cubic feet per minute, as scheduled or as measured.
Take the figure from the equipment schedule, the balancing report or a flow hood reading at the face of the grille. Convert branch by branch rather than converting a system total: a set of L/s figures that all land on round numbers has usually been rounded twice, once by the designer and once here.
Airflow
188.8 L/s
Converted using an exact defined factor of 0.4719474432 L/s per CFM. The arithmetic is exact; a nameplate CFM is not, so convert the airflow you scheduled or measured rather than the one printed on the carton.
- Conversion factor applied
- 0.47 L/s per CFM
They open the calculator with your figures already in it
CFM to Litres per Second Calculator: 189 L/s — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
Show calculation logicHide calculation logic
How this was calculated
Formula source(s)
- 1 ft = 0.3048 m exactly, so 1 ft³ = 0.3048³ m³ = 28.316846592 L exactly. Spread over the 60 seconds in a minute, 1 CFM = 28.316846592 / 60 = 0.4719474432 L/s. That decimal terminates, so the multiplier used here is the exact value with nothing rounded away.
Inputs used
- Airflow (CFM)
- 400
Intermediate steps
- Conversion factor applied
- 0.47 L/s per CFM
Confidence note: Converted using an exact defined factor of 0.4719474432 L/s per CFM. The arithmetic is exact; a nameplate CFM is not, so convert the airflow you scheduled or measured rather than the one printed on the carton.
Add the equipment this sizes
This result is a specification — 188.8 L/s — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.
Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-08-26 · in the site-wide review of 2026-09-06 · v1.0.0
Regulatory standards & verification citations1
- 1 ft = 0.3048 m exactly, so 1 ft³ = 0.3048³ m³ = 28.316846592 L exactly. Spread over the 60 seconds in a minute, 1 CFM = 28.316846592 / 60 = 0.4719474432 L/s. That decimal terminates, so the multiplier used here is the exact value with nothing rounded away.
Cite this page
Your workspace
Most jobs need more than one number. Add the calculators you need next and they open right here, underneath this one — your figures stay on screen and nothing is lost to a page change.
A North American duct schedule speaks CFM, while the consultant's ventilation sheet, the European air handling unit submittal and the commissioning record all want L/s. This page is for the engineer or balancer moving grille and branch duties across that line before a witness test. One trap belongs entirely to this direction: L/s is per second and CFM is per minute, so anyone who converts cubic feet to litres and stops has a number sixty times too large. The other is the mental halving. Calling 1 CFM half a litre per second overstates by 5.9%, and on a 2,000 CFM branch that is 56 L/s of air the system was never asked to move.