AC Tonnage Calculator
Calculate the right AC size based on room dimensions, climate, and heat load factors.
Enter Room Dimensions
Select a room preset or input custom dimensions.
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What is an AC Tonnage Calculator?
An AC Tonnage Calculator determines the cooling capacity (in Tons or BTU) needed for your room based on size, climate, and heat load factors. Choosing the wrong AC size leads to either poor cooling (undersized) or high electricity bills (oversized).
Our calculator accounts for climate zones, insulation quality, occupants, appliances, and structural factors like top floor and sunlight exposure to give you an accurate recommendation.
Results show both BTU (British Thermal Units) and Tonnage, plus equivalent kW rating for easy comparison across brands and regions.
4 Climate Zones
Mild, Warm, Hot, Very Hot/Desert with appropriate multipliers.
Insulation Factor
Poor to Excellent insulation affects cooling load significantly.
Heat Load Factors
Top floor, sunlight, occupants, appliances, kitchen proximity.
BTU + Ton + kW
Multiple capacity units for easy comparison worldwide.
AC Size Quick Reference
| Room Size | Standard | Top Floor | Hot Climate |
|---|---|---|---|
| Up to 100 sq.ft | 0.75 Ton | 1.0 Ton | 1.0 Ton |
| 100-150 sq.ft | 1.0 Ton | 1.5 Ton | 1.5 Ton |
| 150-200 sq.ft | 1.5 Ton | 1.5-2 Ton | 2.0 Ton |
| 200-300 sq.ft | 2.0 Ton | 2.5 Ton | 2.5 Ton |
| 300-400 sq.ft | 2.5 Ton | 3.0 Ton | 3.0 Ton |
* Standard = 10ft ceiling, average insulation, 2 occupants, warm climate
Understanding AC Units
A 1 Ton AC removes 12,000 BTUs of heat per hour
Metric equivalent for cooling capacity
Higher EER = more efficient. Look for EER 3.5+
Standard AC Sizes
AC Buying Tips
Choose inverter AC - 30-50% energy savings over non-inverter.
When in doubt, go higher - 1.5 Ton inverter runs efficiently at 1 Ton load.
Check star rating - 5-star uses 20-30% less power than 3-star.
Consider copper coils - More durable and efficient than aluminum.
Proper installation - Poor installation wastes 10-30% efficiency.
Annual servicing - Dirty filters reduce efficiency by 15-20%.
Why AC Size Matters
⚠️ Undersized AC
- • Runs continuously without cooling properly
- • High electricity bills
- • Compressor overworks and fails early
- • Room never reaches desired temperature
⚠️ Oversized AC
- • Cools too fast, then shuts off (short-cycling)
- • Doesn't remove humidity effectively
- • Frequent on-off damages compressor
- • Wastes energy and money
Frequently Asked Questions
How do I calculate AC tonnage for my room?
Calculate room area (L × W) in sq.ft. Multiply by 20-25 BTU/sq.ft (depending on climate). Add factors for top floor (+20%), sunlight (+15%), occupants (+400 BTU each). Divide total BTU by 12,000 to get tonnage. Example: 150 sq.ft × 20 = 3000 BTU → 0.25 Ton base, but with factors it becomes 1-1.5 Ton.
What size AC do I need for a 12×12 room?
A 12×12 room = 144 sq.ft. In moderate climate with average insulation: needs about 2,880 BTU (0.24 Ton). But with real-world factors (2 people, some sunlight), you'll need 1.0 Ton AC. If top floor in hot climate, consider 1.5 Ton.
What is BTU and how does it relate to AC tonnage?
BTU (British Thermal Unit) measures cooling capacity. 1 Ton AC = 12,000 BTU/hr = 3.517 kW. This means a 1 Ton AC can remove 12,000 BTUs of heat per hour. Higher BTU = more cooling power. Standard AC sizes: 0.75 Ton (9,000 BTU), 1 Ton (12,000 BTU), 1.5 Ton (18,000 BTU), 2 Ton (24,000 BTU).
Should I buy 1 Ton or 1.5 Ton AC?
If your calculation shows 0.9-1.2 Ton, choose 1.5 Ton inverter AC. It can operate at lower capacity (using less power) for normal days but has reserve power for extreme heat. Undersized AC runs continuously without proper cooling. Oversized AC short-cycles and wastes energy.
Why does top floor need more AC capacity?
Top floor rooms receive direct roof heat from the sun, adding 15-25% more heat load. In hot climates, roof temperature can reach 60-70°C, radiating heat into the room below. Always add 20% extra capacity for top floor rooms.
How does ceiling height affect AC sizing?
Standard calculations assume 9-10 ft ceiling. Higher ceilings mean more air volume to cool. Add 5% capacity for each foot above 10 ft. Example: 12 ft ceiling = 10% extra capacity. Lower ceilings (8 ft) can reduce requirement by 5%.
What is an inverter AC and is it better?
Inverter AC varies compressor speed based on cooling need, instead of on/off cycling. Benefits: 30-50% energy savings, consistent temperature, faster initial cooling, quieter operation, longer lifespan. Higher upfront cost but pays off in 1-2 years through electricity savings.
How do occupants affect AC tonnage?
Each person generates ~400 BTU/hr of body heat. Standard calculations assume 2 people. For every additional person, add 400 BTU. Office with 10 people needs 3,200 extra BTUs ≈ 0.27 Ton additional capacity. Server rooms with computers need even more.
Does insulation affect AC size needed?
Yes significantly. Poor insulation (single glazing, gaps) needs 15% more capacity. Excellent insulation (double glazing, insulated walls) can reduce need by 20%. Modern energy-efficient buildings need smaller ACs. Old buildings with poor sealing need larger units.
Can I use this calculator for commercial spaces?
This calculator works for residential and small commercial spaces. For large commercial areas, server rooms, or industrial applications, consult an HVAC professional as factors like ventilation, equipment heat, and process loads require detailed analysis.