How many litres per day dehumidifier do I need?

As a rough guide: rooms up to 15 m² often need 8–10 L/day, normal living rooms 15–25 m² about 12–16 L/day, and large rooms or basements from 30 m² 20 L/day or more. Room temperature, building era and current humidity matter as much as floor area.

Dehumidifier Size Calculator: What Capacity Does Your Room Need?

4 min read · Free, no sign-up

From measurement to litres per day — The calculator turns room volume and humidity into capacity

The "20 litres" on the box sounds impressive – but it only means the unit can extract 20 litres per day under lab conditions (30 °C / 80 % humidity). In your living room at 20 °C it often manages half that. This calculator matches your room data against typical real-world values.

Your room

Room area (m²)

Ceiling height (m)

Room type

Windows / building era

Current humidity

Room temperature

Electricity price (ct/kWh) Only affects the running-cost estimate, not the sizing

How the calculator works We estimate the daily water load from room volume, room type, window airtightness and measured humidity. Manufacturer ratings usually apply to 30 °C / 80 % – real rooms run below that, so expect roughly 50–60 % of the rated figure. This is an experience-based estimate, not a substitute for a survey if you have leaks or structural damp.

Related guides

Drying clothes with a dehumidifier
Dehumidifier vs tumble dryer
Heated airer running costs
Deutsche Version: Luftentfeuchter-Rechner

FAQ

How many litres per day do I need?

Rough guide: up to 15 m² often 8–10 L/day, 15–25 m² about 12–16 L/day, from 30 m² 20 L/day or more. Temperature, building era and current humidity matter as much as area.

Is a cheap Peltier dehumidifier enough?

Peltier units extract only 0.3–0.8 L/day and suit tiny, moderately damp rooms. For persistent 70 %+ humidity you need a compressor unit.

Which dehumidifier for a cold basement?

Below 15 °C compressor units lose capacity. Desiccant models are the better choice in cold basements.