Ceiling Fan Size Calculator
The right diameter, the correct mounting type and what it costs to run – all from your room dimensions.
All values are guidance figures. The diameter recommendation follows common practice (at least 2.30 m floor clearance, 50 cm to walls, 30–50 cm to the ceiling). Power draw is a typical value for the motor type – your model data sheet has the exact figure.
How the calculator picks the diameter
The recommendation follows the established scale by room area. What matters is not motor power but swept area: it grows with the square of the diameter, which is why a large fan on a low speed moves the same air as a small one on high – only quieter and using less power.
- up to 10 m² – 75 to 105 cm
- 10 to 15 m² – 105 to 120 cm
- 15 to 25 m² – 120 to 140 cm
- 25 to 35 m² – 140 to 150 cm
- over 35 m² – two units, one per zone of use
The calculator also checks wall clearance: blade tips need at least 50 cm to every wall. In a narrow room that caps the possible size regardless of floor area – a warning appears in that case.
Mounting type and downrod length
The target is a blade plane roughly 2.60 to 2.70 m above the floor. That determines the mounting type:
- below 2.40 m – too low; a ceiling fan is usually the wrong solution here
- 2.40 to 2.55 m – flush mount (hugger), no downrod
- 2.55 to 2.85 m – standard mounting with the shortest supplied rod
- above that – downrod, with the length given by the calculator
Running costs
Power draw depends mainly on the motor type. DC motors are markedly more efficient at partial load – which is exactly where fans run in everyday use. The calculator uses typical figures: DC around 6 W on low, 18 W on medium and 35 W on high; AC roughly 20, 40 and 60 W.
For comparison a portable air conditioner at 1,000 W is calculated over the same usage. The difference is typically a factor of 30 to 50.
Frequently asked questions
Can a ceiling fan be too large?
Too much airflow is not a problem – you simply turn the speed down. Too large in terms of clearance is: if blade tips come closer than 50 cm to a wall, the fan gets loud and airflow suffers.
Why two fans instead of one big one?
From roughly 35 m² upwards, two smaller units distribute air more evenly, run quieter and can be used selectively. Space them about two diameters apart.