Dehumidifier size calculator
What size dehumidifier do you need?
Seven quick questions. We work out how much water your space collects each day in Sri Lankan air, then match it to a DRYAir unit, and show you the working.
Our recommendation
DRYAir DA-35L
Rs. 209,000
Covers 35–80 m² per unit
12.2 L
of water a day to remove
22.5 L
it removes a day here, at 55%
Other options that also work
- 2 × DA-12LC15.4 L/day · Rs. 218,000
- 2 × DA-20L20.4 L/day · Rs. 298,000
- DA-50L30.8 L/day · Rs. 249,000 · more headroom
How it works
Sized for Sri Lankan air, not American basements
Most calculators online use the US industry chart, which sizes by floor area for cool, closed basements. Here the problem is the air outside: at 28°C and 80% humidity it holds about 22 g of water in every cubic metre, and some of it seeps into every building, all day.
- 1
Water coming in
Your space's volume, how much outside air gets in (doors, windows, AC), and the difference between Sri Lankan air and a space held at 55%.
- 2
Water made inside
People, laundry and cooking, plus extra for spaces that are already wet, scaled from the industry chart's dampness levels.
- 3
What each unit really removes
Worked out for your space's temperature from each model's two rating-plate figures, with a 20% safety margin.
- 4
Checked twice
Every answer must also fit the coverage on our product pages and pass the US industry chart.
Questions people ask
What size dehumidifier do I need for an office or store in Sri Lanka?+
A closed, air-conditioned office of about 400 sq ft (37 m²) usually needs a DRYAir DA-20L, and a small server space or cabin often needs only a DA-12LC. Stores and warehouses with doors that stay open, or spaces with visible mould, step up to a DA-35L or DA-50L. The calculator works it out from your own measurements.
What size dehumidifier do I need for a bedroom in Sri Lanka?+
For a typical 120–180 sq ft bedroom that's kept closed, a DRYAir DA-12LC is usually enough. If the space has no AC and the windows are often open, or there's visible mould, the calculator will usually step you up to a DA-20L or larger.
Why does this calculator recommend a bigger unit than US calculators?+
US calculators use the AHAM chart, which was built for cool, closed basements. Outdoor air in Colombo carries about twice as much water as a US basement's, and it leaks in all day, so spaces here need more capacity for the same floor area. We check the AHAM chart too, but only let it make the answer bigger.
What do the litres per day ratings mean?+
A rating like 20 L/day is measured in hot, very humid test air (30°C, 80% humidity). In a space being held at 55%, every dehumidifier removes less than its rating, so the calculator works out what each model actually removes in your conditions.
What humidity should I keep indoor spaces at?+
Between 40% and 60%. Mould and dust mites struggle below 60%, and DRYAir units are set to hold spaces at about 55%.
Can one dehumidifier do a whole apartment or office suite?+
Only the spaces it can reach. If the internal doors stay open, one larger unit in a central spot can cover a small apartment or office suite. If cabins or bedrooms are kept closed, a smaller unit in each problem space works better.