How to Choose the Right AC Size for Your Room
Quick answer: Measure the floor area of the room in square feet, then match it to a tonnage chart for hot summers. Haier’s sizing guide puts rooms up to 150 square feet at 1 ton, rooms of 151 to 250 square feet at 1.5 ton, and rooms of 251 to 400 square feet at 2 ton. Then adjust for a high ceiling, strong sun, the number of people and kitchen use. A 1.5 ton split AC suits a typical bedroom of about 151 to 250 square feet.
What tons and BTU mean for an air conditioner
Cooling capacity is measured in British thermal units (BTU) per hour. Split ACs in Pakistan are usually sold by the ton, and Haier’s guide explains that one ton is approximately 12,000 BTU. A 1 ton unit is therefore about 12,000 BTU per hour, a 1.5 ton unit about 18,000 and a 2 ton unit about 24,000. The 1.5 ton models in our range are listed at 18,000 BTU per hour on their product pages.
Step 1: Measure the room in feet
Measure the length and width of the room in feet. ENERGY STAR suggests converting inches into fractions of a foot, so 12 feet 6 inches becomes 12.5 feet. Multiply length by width to get the floor area in square feet.
For example, a room that is 12.5 feet by 14 feet has an area of 175 square feet.
Step 2: Find your room in the tonnage chart
Find your floor area in the first column, then read the size beside it. These figures come from Haier’s guide to AC tonnage, which assumes a ceiling of 8 to 9 feet.
| Room size (square feet) | AC size | About (BTU per hour) |
|---|---|---|
| Up to 150 | 1 ton | 12,000 |
| 151 to 250 | 1.5 ton | 18,000 |
| 251 to 400 | 2 ton | 24,000 |
The 175 square foot room from the example falls in the 151 to 250 row, so its starting size is 1.5 ton.
Step 3: Adjust for your room
The chart is a starting point. Haier’s guide lists these adjustments:
- If the ceiling is high, add 10 percent to the cooling capacity.
- If the room gets strong sun through south or west facing windows, increase the capacity by 10 to 20 percent. A shaded room facing north or east needs only the standard capacity.
- Add about 0.1 ton for each person above two who regularly uses the room.
- For a kitchen, or an office with many appliances and lights, add about 0.5 ton.
ENERGY STAR gives similar advice: it suggests reducing the capacity by 10 percent for a heavily shaded room, adding 600 BTU per hour for each regular occupant above two, and adding 4,000 BTU per hour for a kitchen.
Using the same 175 square foot room: if a west window gets the afternoon sun and four people use the room, 1.5 ton goes up by 10 to 20 percent to about 1.65 to 1.8 ton. Two additional people add about 0.2 ton, which gives roughly 1.85 to 2 ton. That room is better served by a 2 ton unit than a 1.5 ton one.
How our AC size calculator works
Our AC size calculator follows the same idea, so you can check a room in a few seconds. It uses about 80 BTU per hour for each square foot at a 10 foot ceiling, which is the same as 1 ton for 150 square feet. It then scales the figure for your ceiling height, takes off 10 percent for a shaded room or adds 20 percent for a very sunny or top floor room, adds 600 BTU per hour for each person above two, and adds 4,000 BTU per hour for a kitchen. Finally it rounds up to the nearest standard size: 1, 1.5, 2, 2.5, 3 or 4 ton.
What size fits our split ACs?
Every split AC in our current range is a 1.5 ton model, rated at 18,000 BTU per hour. On Haier’s chart, 1.5 ton matches a room of about 151 to 250 square feet, which covers most bedrooms and small lounges. For example, a bedroom of 14 by 16 feet is 224 square feet, which sits in that row.
A small room of up to 150 square feet usually needs only 1 ton, and a room above 250 square feet, or a sunny room with several people, may need 2 ton. If your room falls outside the 1.5 ton row, ask the branch which models are available before you buy. Our branch staff can check the room size with you.
Why a bigger air conditioner is not better
ENERGY STAR explains that a unit that is too large will be less effective and less efficient. It cools the room before it has time to remove humidity. The result is cool, moist air that makes the room feel damp and clammy. The most energy-efficient air conditioner is the one sized to the room it cools, so do not choose a larger unit only to be safe.
Why some charts show much smaller sizes
You may see the ENERGY STAR sizing chart, which lists only 5,000 BTU per hour for a room of 100 to 150 square feet. That chart is written for room air conditioners sold in the United States. Haier’s guide for India, a market with hot summers like ours, uses the larger figures in the table above, and our calculator follows that approach. Use the ENERGY STAR page for its advice on oversizing, shade and occupants, and use the tonnage chart for the size itself.
Ceiling height and where the unit goes
The tonnage chart assumes a ceiling of 8 to 9 feet. A taller ceiling means more air to cool, so add 10 percent, or enter the real height in our calculator. ENERGY STAR also advises that when a unit is mounted near a corner of the room, you should choose a unit that can direct the airflow where you need it.
Four worked examples
The examples below use the same steps as the guide. Each one starts from the floor area, reads the tonnage chart, and then applies the adjustments.
| Room | Area (sq ft) | Chart size | Adjustments | Suggested size |
|---|---|---|---|---|
| Small bedroom, 12 by 12 ft, shaded, two people | 144 | 1 ton | None | 1 ton |
| Bedroom, 14 by 16 ft, normal sun, two people | 224 | 1.5 ton | None | 1.5 ton |
| Bedroom, 14 by 16 ft, west window, three people | 224 | 1.5 ton | Sun: +10 to 20%. One person above two: +0.1 ton | About 1.75 to 1.9 ton, so 2 ton |
| Lounge, 15 by 20 ft, normal sun, two people | 300 | 2 ton | None | 2 ton |
The second room is the closest match for our 1.5 ton models. The first room needs a smaller unit, and the third and fourth rooms need a larger one.
Checklist before you buy
- Measure the floor area in feet, and convert inches into fractions of a foot.
- Read the starting size from the tonnage chart, then apply the ceiling, sun, people and kitchen adjustments.
- Note the ceiling height. The chart assumes 8 to 9 feet, so a higher ceiling needs about 10 percent more.
- Decide where the outdoor unit will go, and where the indoor unit will blow the air.
- Ask the branch who handles installation and service in your area, and keep the warranty card with the receipt.
Common mistakes
- Choosing a larger unit to be safe. ENERGY STAR explains that an oversized unit removes less humidity, which leaves the room damp and clammy.
- Ignoring the sun. Haier’s guide adds 10 to 20 percent for a room with strong sun through south or west facing windows.
- Forgetting the people and the kitchen. Each regular occupant above two adds about 0.1 ton, and a kitchen adds about 0.5 ton.
- Measuring the wrong space. Measure the room the unit will cool, not the whole flat or house.
Frequently asked questions
What size AC do I need for a 12 by 12 room?
A 12 by 12 foot room is 144 square feet. Haier’s chart puts rooms up to 150 square feet at 1 ton, which is about 12,000 BTU per hour. Add more for strong sun, a high ceiling or extra people.
Is a 1.5 ton AC right for a bedroom?
For a bedroom of about 151 to 250 square feet, yes. That is the 1.5 ton row in Haier’s chart. A small bedroom of up to 150 square feet usually needs only 1 ton.
Does sunlight change the size I need?
Yes. Haier’s guide adds 10 to 20 percent for a room with strong sun through south or west facing windows, and ENERGY STAR suggests 10 percent less for a heavily shaded room.
Does a kitchen need a bigger unit?
Yes. Haier’s guide adds about 0.5 ton for a kitchen with high appliance use, and ENERGY STAR suggests adding 4,000 BTU per hour when the unit is used in a kitchen.
Why does the ENERGY STAR chart show smaller sizes?
The ENERGY STAR chart is written for room air conditioners sold in the United States. For hot summers, manufacturer guides such as Haier’s use larger sizes per square foot, and our calculator follows that approach.
Can I check the size online?
Yes. Use our AC size calculator to get a starting size, then confirm it with the branch before you buy.
Next steps
Measure the room, read the chart, make the adjustments, and then look at our split AC range. Each product page lists the capacity, the type and the colour choices. If the size you need does not match a model we stock, ask our branch staff before you buy. To compare compressor types, read our guide to inverter AC vs normal AC.
Sources
- Haier India, How to Calculate the Perfect AC Tonnage for Your Room (tonnage chart, ceiling, sun, occupant and kitchen adjustments): haier.com, AC tonnage guide
- ENERGY STAR, Room Air Conditioners (measuring, oversizing, shade, occupant and kitchen guidance): energystar.gov/products/room_air_conditioners