Air Conditioning Size Calculator
Wondering what size air conditioner you need? Enter your room dimensions, ceiling height, room type and window details below — our calculator will recommend the right cooling capacity in kW for your space.
How our air conditioning size calculator works
Our calculator uses industry-standard cooling load estimation to recommend the right unit size for your space. The calculation starts with the volume of your room (floor area × ceiling height) and applies a fabric heat load of 40 W per cubic metre, adjusted by a room-type factor. Kitchens, server rooms and heavily glazed spaces carry higher factors because they generate or absorb more heat.
Window solar gain is then added based on the area and orientation of each window. South-facing glazing contributes the most heat load, while north-facing windows contribute very little. The total cooling load in watts is converted to kilowatts, and we round up to the nearest standard unit size to ensure your system can handle peak demand.
Factors that affect air conditioning sizing
Room volume is the starting point, but several other factors influence the cooling capacity you need:
- Insulation quality — well-insulated rooms retain conditioned air better, reducing the required capacity.
- Occupancy — each person in a room adds roughly 100–150 W of heat.
- Electrical equipment — computers, lighting and appliances all generate heat that the AC must counter.
- Solar gain through windows — south and west-facing glazing significantly increases cooling load in summer.
- Room type — kitchens and server rooms have higher base loads due to equipment heat output.
Standard air conditioning unit sizes explained
Air conditioning units are typically available in the following cooling capacities:
- 2.5 kW — small bedrooms, home offices and garden rooms up to ~15 m²
- 3.5 kW — standard bedrooms and small meeting rooms up to ~25 m²
- 5.0 kW — living rooms, larger offices and meeting rooms up to ~40 m²
- 7.0 kW — open-plan spaces, small halls and retail units up to ~55 m²
- 10.0 kW — large commercial spaces, halls and showrooms
- 14.0 kW — very large spaces requiring a single high-capacity unit
For larger commercial spaces, multi-split and VRF (variable refrigerant flow) systems can combine multiple indoor units served by a single outdoor condenser, offering greater efficiency and zone control.
Get your air conditioning installed by professionals
Ready to enjoy year-round comfort? Our F-Gas certified, MCS-certified engineers install air conditioning systems across the East Midlands — from offices, shops and commercial premises to churches, village halls and heritage buildings. We handle everything from unit selection through to final commissioning, with discreet pipework that respects the character of your building.