Updated 21 August 2026
A dehumidifier is rated in pints per day, and in 2019 the test that produces that number changed. Most sizing advice online was written before then and never updated. We publish both scales and say which one every figure is on.
| Space | Condition | Buy today | Old chart |
|---|---|---|---|
| 500 sq ft | very damp | 9 pt/day | 12 pt/day |
| 1,000 sq ft | very damp | 11 pt/day | 16 pt/day |
| 1,500 sq ft | wet | 16 pt/day | 22 pt/day |
| 2,000 sq ft | wet | 18 pt/day | 26 pt/day |
Same requirement, two labels. Read an old chart’s number as a modern one and you buy about 41% more machine than you need — a 70-pint unit on the old scale is labelled 50 today.
Size it on pints per day, on both rating scales.
Picks checked against tested capacity, never coverage claims.
How the numbers work, and which ones lie.
Head to head, on evidence we can check.
A cobalt-chloride humidity indicator card — the strip people tape inside a crawl space — is blue when the air is dry and turns pink as it takes up moisture. It is an ordered scale you can read at a glance, so the site uses it. Below 50% is where you want to be; above 60% is where mould grows.
DRY → HUMID · %RH indicated