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.
🧊 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.