SettingsSettings for this calculationUS
The airflow duty in litres per second, from the metric schedule.
Room extract rates, supply duties and per-person rates in metric specifications are almost always written in L/s. Enter the duty for the item you are actually selecting — the fan has to carry the total plus system leakage, while a single grille only ever sees its own share.
Airflow
529.7 CFM
Converted using an exact defined factor of 2.118880003289315 CFM per L/s. Exact to the limit of the decimal shown, but converting a duty is not selecting a fan — re-check the chosen wheel against your own external static pressure once the number is in CFM.
- Conversion factor applied
- 2.12 CFM per L/s
They open the calculator with your figures already in it
Litres per Second to CFM Calculator: 530 CFM — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
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How this was calculated
Formula source(s)
- This is the reciprocal of 0.4719474432. Exactly, 1 L/s = 60 / 28.316846592 = 39062500 / 18435447 CFM = 2.118880003289315…, and that decimal repeats rather than terminating. The definition underneath it (1 ft = 0.3048 m exactly) is exact, but the multiplier shown here is that exact fraction rounded — at 16 significant figures, so the rounding is nowhere near any airflow you will ever meter.
Inputs used
- Airflow (L/s)
- 250
Intermediate steps
- Conversion factor applied
- 2.12 CFM per L/s
Confidence note: Converted using an exact defined factor of 2.118880003289315 CFM per L/s. Exact to the limit of the decimal shown, but converting a duty is not selecting a fan — re-check the chosen wheel against your own external static pressure once the number is in CFM.
Add the equipment this sizes
This result is a specification — 529.7 CFM — 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
- This is the reciprocal of 0.4719474432. Exactly, 1 L/s = 60 / 28.316846592 = 39062500 / 18435447 CFM = 2.118880003289315…, and that decimal repeats rather than terminating. The definition underneath it (1 ft = 0.3048 m exactly) is exact, but the multiplier shown here is that exact fraction rounded — at 16 significant figures, so the rounding is nowhere near any airflow you will ever meter.
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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.
Ventilation duties across the UK, Ireland, Scandinavia and Australasia are written in L/s, but fan curves, sone ratings, throw data and filter selections from North American manufacturers are published in CFM against inches of water gauge. This page serves the designer or estimator holding a metric duty and reading an imperial catalogue. The trap that belongs to this direction alone is the doubling habit: two CFM per litre per second lands 5.6% low, so a 500 L/s riser converts to 1,059 CFM rather than the 1,000 you assumed, and 59 CFM is often the gap between one wheel size and the next one up.