Free UK sizing calculator
Dehumidifier size calculator
Compare 10L, 12L, 20L and 25L capacity classes using the space, humidity, temperature and moisture task you actually need to manage.
Capacity class to compare first
Compare a mid-capacity model with a 20L-class model so you can weigh size and noise against recovery headroom.
- 48 m³ is in this helper's smaller-room volume band.
- 68% RH adds moderate capacity headroom.
- Regular window condensation adds recovery demand beyond an occasional high reading.
- Volume screen
- Up to 50 m³
- Humidity
- +½ moderate-RH adjustment
- Moisture task
- +½ moisture-load adjustment
The litres-per-day label is a rated-condition category, not a promise of daily collection in your room.
Method, not magic
A transparent screen for the first models to compare.
The calculator starts with managed room volume: up to 50 m³, over 50 to 100 m³, or over 100 m³. It then adds capacity headroom for readings at or above 65% RH and for repeated condensation, persistent damp signs or indoor laundry.
Temperature does not silently inflate the answer. Below 15°C the result instead tells you to compare compressor and desiccant technology, because buying a bigger compressor model may not address cold-condition performance.
This produces a comparison class, not an engineering specification or a guarantee. Open doors, moisture entering the room, fan airflow, target RH, layout and the time available to recover all matter. Read the complete dehumidifier sizing guide before buying.
Why room conditions matter
The model name is not the normal-room extraction result.
The table uses one current manufacturer range to show the scale of the difference. It is not a universal performance table for every model in each capacity class.
| Meaco Arete Two class | 10°C / 60% RH | 20°C / 60% RH | Published input at 20°C / 60% RH |
|---|---|---|---|
| 10L | 1.38 L/day | 4.19 L/day | 136 W |
| 12L | 1.97 L/day | 5.40 L/day | 136 W |
| 20L | 3.35 L/day | 8.50 L/day | 207 W |
| 25L | 3.55 L/day | 10.85 L/day | 250 W |
A 25L badge therefore does not mean 25 litres will be collected from a typical room every day. Compare exact candidates at the same test condition.
Sizing questions
Questions to settle before checkout.
What size dehumidifier do I need for one room?
For one normally heated room with a light moisture load, 10L and 12L classes are sensible starting points. A larger room, repeated condensation or frequent laundry can justify comparing 16L to 20L models. Check condition-specific extraction rather than treating the model name as promised daily collection.
Is a 20L dehumidifier too big for a bedroom?
Not automatically, but it may bring more size, noise and hourly power than the room needs. Compare it with a 10L or 12L model using the same temperature and humidity condition, then consider recovery time and how often it will run.
Should I buy a bigger dehumidifier for a cold room?
Not before comparing technologies. Compressor extraction falls in cooler conditions, so a desiccant model may be the better comparison for a regularly cold or unheated room. A larger compressor label alone does not solve that mismatch.
Does a 20L dehumidifier remove 20 litres every day?
Not in every home. The rating is measured under specified conditions. Current Meaco Arete Two data, for example, states 8.50 L/day at 20°C and 60% RH for its 20L model, illustrating how ordinary-room performance can differ from the name.
Source trail
Check the comparison data.
Manufacturer specifications were checked on 20 September 2026. Product specifications can change, so inspect the current pages before buying.