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Sizing and running-cost tools

Three calculators, each showing its working. Nothing you enter leaves your browser.

What are you seeing? (optional, tick any)

Condensation on windowsVisible mouldA musty smellLaundry takes ages to dryWet patches, tide marks or peeling paintDust, pets or hay feverSmoke, cooking smells or traffic fumes

Floor area to treat (m²)

Length × width in metres. For several connected rooms, add them up.

How warm is the space?

Anything that adds moisture or people?

I dry laundry indoors regularly Heavy damp: visible mould, musty smell or streaming windows Four or more people at home

Room length (m)

Room width (m)

Ceiling height (m)

What's it for?

Size to the room the purifier will actually run in, not the whole home.

Power (watts)

From the label or spec sheet. Use the maximum for a worst case.

Hours running per day

Electricity price (p per kWh)

Pre-filled with the October 2026 price cap, as quoted by Which?. Change it to match your tariff.

Rated litres per day (optional)

Gives a cost per litre extracted.

How these calculators work

Dehumidifier sizer: a points score from floor area, laundry, damp, occupants and cold. Read the method in What size dehumidifier do I need?
Air purifier calculator: required CADR equals room volume times target air changes per hour. See Air purifier room size and CADR.
Running-cost calculator: watts ÷ 1,000 × hours × price per kWh. See Dehumidifier running costs.

Airsum

Dehumidifier and air purifier sizer for UK homes. Independent: we don't sell or stock anything.

info@airsum.co.uk

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