Free room AC size estimator
AC Tonnage Calculator for Room Size, BTU and Electricity Use
Estimate the cooling capacity your bedroom, living room or office may need. Enter your room dimensions, climate and daily usage to get an AC size in tons, BTU per hour and approximate monthly energy consumption.
- Mobile friendly
- BTU and tonnage result
- Energy cost estimate
Calculate AC Tonnage
For a final HVAC decision, confirm the result with a qualified technician.
1 ton = 12,000 BTU/hr
AC Size Guide by Room Area
Room area is only the starting point. Sunlight, ceiling height, insulation, climate and number of people can push the recommended air conditioner size up or down.
| Room Area | Typical AC Size | Best Use | Extra Check |
|---|---|---|---|
| Up to 100 sq ft | 0.75 to 1 ton | Small bedroom, study room | Choose higher size for top-floor rooms. |
| 100 to 150 sq ft | 1 to 1.25 ton | Standard bedroom | Strong sunlight may need the next size. |
| 150 to 220 sq ft | 1.5 to 2 ton | Master bedroom, small hall | Check ceiling height and window area. |
| 220 to 320 sq ft | 2 to 2.5 ton | Large room, office cabin | Airflow layout matters as much as tonnage. |
How to Choose the Right AC
Do Not Oversize
A very large AC can cool quickly but may short-cycle, use more power and remove less humidity. A correctly sized inverter AC usually gives steadier comfort.
Check Efficiency
Higher efficiency models consume less electricity for the same cooling output. Compare star labels, ISEER or COP values before buying.
Improve the Room
Curtains, sealing air gaps, cleaning filters and reducing afternoon sunlight can lower the cooling load before you spend on a bigger unit.
Inverter vs Non-Inverter AC
| Feature | Inverter AC | Non-Inverter AC |
|---|---|---|
| Compressor speed | Variable speed for steady cooling | Fixed on/off cycles |
| Energy use | Often lower during regular daily use | Usually higher for long operating hours |
| Comfort | Better temperature stability | More temperature swings |
| Best for | Bedrooms, offices and frequent use | Occasional use and smaller budgets |
AC Tonnage Calculator FAQ
How is AC tonnage calculated?
A common estimate starts with room area multiplied by about 20 BTU per sq ft, then adjusts for ceiling height, people, sunlight, insulation and climate. The BTU result is divided by 12,000 to convert it into tons.
What size AC is best for a 150 sq ft room?
Many 150 sq ft rooms fall around 1 to 1.5 ton, but hot climates, poor insulation, top-floor rooms or direct sunlight can increase the needed size.
How do I estimate AC electricity bill?
Multiply estimated input power in kW by daily hours and monthly days, then multiply by your electricity rate per unit. This calculator uses the selected efficiency level to estimate input power.
Is a 1.5 ton AC enough for a 200 sq ft room?
It may be enough for a well-insulated room in a moderate climate. For hot cities, strong sunlight or high ceilings, 2 ton may be more suitable.