Exhaust Fan Sizing — CFM Calculator for Singapore Bathrooms

How the rule works

The international standard is 1 CFM per square foot of bathroom floor area, with the fan running 8 air-changes per hour. In Singapore's 80–90% humidity that's not enough — we apply a 1.5x uplift for tropical conditions. If your bathroom has a soaking tub or two showers, add another 50 CFM per fixture. For ceilings over 2.7 m, multiply the result by (ceiling height in m / 2.4).

HowTo: use the calculator above

Step 1 — measure your bathroom floor area in square metres (length × width). Step 2 — count fixtures: standard shower = 1, soaking tub = 2, double rainfall = 2. Step 3 — note ceiling height (most HDB = 2.6m, condo = 2.7–3m). Step 4 — read the recommended CFM and the matching KDK/Panasonic model in the results.

Common results for Singapore homes

HDB 4-room master bath (4.5 m², standard shower, 2.6m ceiling) — 75 CFM, KDK 24CDQN equivalent. HDB common bath (2.5 m²) — 50 CFM, KDK 17CUG. Condo master with rainfall + handheld (6.5 m², 2.8m) — 130 CFM, Panasonic FV-13VK3 or twin-fan. Landed family bath with tub (8 m², 3m) — 170 CFM, requires inline.

When the result says you need an inline fan

Above ~130 CFM, ceiling-mount fans become loud (>3 sone). Switch to an inline fan installed in the false ceiling void — quieter, more efficient, and easier to duct to outside. Inline + humidistat is our default recommendation for any Singapore bathroom over 5.5 m².

For surface mould you can already see, jump straight to professional mould removal in Singapore. For the full topic, see the Bathroom Exhaust Fan Singapore pillar.

Frequently Asked Questions

Why does Singapore need a higher CFM than international standards?

Because 80–90% outdoor humidity means the air being pulled in to replace bathroom air is already moist. You need higher extraction to maintain the same drying rate. Our 1.5x uplift matches what we see in the field across HDB, condo and landed jobs.

Can I use a smaller fan if I leave it running longer?

Marginally. A fan rated 50 CFM running for 60 minutes moves the same volume as a 100 CFM fan in 30 minutes, but it does so at lower air velocity — moisture has more time to condense on surfaces before being extracted. Always size for short-duration high-velocity extraction.

Does the calculator account for double-vanity layouts?

Yes — double vanity adds about 10% to moisture load (from shaving, hand-washing). The +50% humidity uplift already covers this; no separate adjustment needed.

Got your CFM number? Book installation from $380 — supply + fit + 1-year warranty.

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