AC tonnage is one of the most important specifications when choosing an air conditioner, yet many people don't understand what it really means or why it matters.
What Does Tonnage Mean in AC?
Tonnage refers to the cooling capacity of an air conditioner. It's measured in "tons" of refrigeration, where:
- 1 ton = 12,000 BTU/hour of cooling capacity
- A 1.5 ton AC = 18,000 BTU/hour
- A 2 ton AC = 24,000 BTU/hour
- A 2.5 ton AC = 30,000 BTU/hour
The term "ton" comes from the historical definition of cooling needed to melt one ton of ice in 24 hours.
Why Tonnage Matters
Tonnage directly determines your AC's cooling power. It's the single most important factor in choosing the right AC:
Undersized AC (Wrong Tonnage)
- Runs constantly without reaching set temperature
- Higher electricity bills due to continuous operation
- Poor dehumidification
- Shorter lifespan from overwork
Oversized AC (Wrong Tonnage)
- Cools room too quickly
- Short cycles (turns on/off frequently)
- Poor humidity control
- Higher energy consumption despite quick cooling
How to Determine Your Tonnage Needs
The basic rule of thumb:
Required BTU = Room Size (sq ft) × 25 = Tonnage = BTU ÷ 12,000
For example: A 200 sq ft room needs 200 × 25 = 5,000 BTU = approximately 0.5 tons
Tonnage by Room Size
Quick reference guide:
- 100-150 sq ft: 0.75 ton (9,000 BTU)
- 150-250 sq ft: 1 ton (12,000 BTU)
- 250-400 sq ft: 1.5-2 tons (18,000-24,000 BTU)
- 400-600 sq ft: 2-2.5 tons (24,000-30,000 BTU)
- 600-800 sq ft: 3-4 tons (36,000-48,000 BTU)
Tonnage Adjustments for Special Conditions
Room size alone doesn't tell the whole story. Consider these factors:
Add Tonnage If:
- High ceiling (above 10 feet): Add 10-20%
- Lots of sun exposure: Add 10%
- Many occupants: Add 5% per extra person
- Kitchen adjacent: Add 10%
- Poor insulation: Add 10-15%
Reduce Tonnage If:
- Well-insulated room: Subtract 5-10%
- Shaded room: Subtract 5%
- Modern/sealed windows: Subtract 5%
Inverter vs Non-Inverter and Tonnage
Inverter ACs can handle slight oversizing better than non-inverter ACs. If you're between two sizes:
- Inverter AC: Choose the larger size for comfort
- Non-Inverter AC: Choose the smaller size to avoid short cycling
Common Tonnage Mistakes
Mistake #1: "Bigger is Always Better"
Many people assume a larger tonnage means better cooling. This is false. Oversized AC creates humidity issues and wastes electricity.
Mistake #2: Ignoring Climate Differences
In extremely hot climates (40°C+), you may need to size up by 10-20% from the standard formula.
Mistake #3: Not Accounting for Equipment Heat
Rooms with computers, servers, or other electronics generate extra heat that increases cooling requirements.
How to Find Your AC Tonnage
If you already have an AC and want to know its tonnage:
- Check the nameplate on your outdoor unit
- Look for "capacity" or "BTU" rating
- Divide BTU by 12,000 to get tonnage
- Alternatively, use our BTU calculator tool
Conclusion
Tonnage is the foundation of AC selection. Getting the right tonnage for your specific room ensures comfort, efficiency, and longevity. Use our free calculator to determine your exact needs, then factor in climate, insulation, and usage patterns.