Need to size the air conditioning for an office? Offices gain heat from computers, lighting, and people, giving a cooling factor around 20 BTU/sq ft. Comfortable, quiet cooling directly affects productivity, so office AC should be sized for a full working day with all equipment running. The calculator below is pre-set to a office at 300 sq ft — a office that size typically needs about a 0.75 Ton AC (7,260 BTU/hr, 2.1 kW) in a moderate climate. Enter your own area for an instant answer.
Unique HVAC Demands for a Office
When calculating the AC tonnage for a Office, standard residential square-footage rules of thumb will lead to disastrously incorrect sizing. This is because a Office introduces highly specific internal heat loads, specifically: computers, copiers, and dense cubicle occupancy with large perimeter windows.
Office AC sizing must account for the specific solar heat gain of large glass facades and the internal heat load of IT equipment. Variable Refrigerant Flow (VRF) systems are highly recommended to provide simultaneous heating and cooling to different zones. Use the calculator below to factor in these unique commercial variables and get an accurate estimate of the required cooling capacity.
🧊 Find the Right AC Size for Your Room — in Tons & BTU
Convert room size (sq ft or m²) to the exact AC tonnage you need — 0.5, 1, 1.5, 2 Ton and up. ACCA Manual-J inspired, in tons, BTU/hr and kW, for the US, UK, Europe, India, UAE, Saudi Arabia & Australia.
🌍 Prefer metric? Switch units here
🏠1. Space Type
📐2. Floor Area & Ceiling
Range: 50 – 10,000 sq ft
Range: 7 – 20 ft
Range: 0 – 50 people
🌍3. Country / Climate
The base factor assumes a 30 °C / 86 °F design day. Change the chip above to match your region.
🧱4. Insulation
☀️5. Sun Exposure
🪟6. Windows / Glazing
➕Advanced loads (kitchen, appliances, exhaust) — optional
Wattage × 3.4 = BTU/hr. e.g. 500 W ≈ 1,700 BTU/hr
For office IT, gym gear, lab equipment
Office AC Size by Floor Area
Typical AC tonnage for an office with an 8-foot ceiling and average conditions. Heavy equipment, high occupancy, or a hot climate will push these up — adjust those in the calculator:
| Office Size | Recommended AC | Approx. BTU/hr |
|---|---|---|
| 150 sq ft | 0.5 Ton | 3,630 BTU/hr |
| 300 sq ft | 0.75 Ton | 7,260 BTU/hr |
| 500 sq ft | 1.5 Ton | 12,100 BTU/hr |
| 800 sq ft | 2 Ton | 19,360 BTU/hr |
| 1,200 sq ft | 2.5 Ton | 29,040 BTU/hr |
Sizing AC for a Office — What to Consider
Add computer and equipment heat with the equipment field, and size for peak staff occupancy. Open-plan offices often benefit from multiple zones or a multi-split so meeting rooms and the main floor can be controlled separately. The calculator applies the office heat-gain factor automatically; use the advanced fields (occupants, equipment, appliances, ventilation) to match your exact space, and remember an oversized unit short-cycles and dehumidifies poorly — right-sizing gives better comfort and lower running cost.
Frequently Asked Questions
What size AC do I need for an office? An 300 sq ft office typically needs about a 0.75 Ton AC (7,260 BTU/hr) in a moderate climate; scale up or down with your floor area per the chart above.
What size AC for an office? About 20 BTU/sq ft plus computers and occupants. A 300 sq ft office typically needs around 0.75–1 ton with equipment load added.
How many BTU per square foot for an office? Roughly 20 BTU/sq ft as a starting factor, before adjusting for climate, ceiling height, occupancy, and equipment heat.
Background reading: how the refrigeration cycle works.
Estimates vary by contractor. Compare free quotes from licensed local pros before you commit. Request a quote →
High-efficiency systems may qualify for utility rebates and federal or state incentives. Find current programs at ENERGY STAR & DSIRE.
Figures are reviewed by the Refcon HVAC engineering team using U.S. DOE, ENERGY STAR & ACCA Manual J data. Estimates only — confirm with a licensed pro.