How to use the AC tonnage calculator
- 1 Enter the room length and width in feet.
- 2 Enter the ceiling height.
- 3 Choose top floor or west-facing if the room gets extra heat.
- 4 Enter the people and whether there is a kitchen.
Worked example
A 14 × 12 ft bedroom with a 10 ft ceiling, not on the top floor, for two people. The cooling load is about 11,760 BTU per hour, just under one ton, so a 1 ton AC is recommended. On a top floor the load rises to about 14,100 BTU, so a 1.5 ton unit would be better.
Choosing and running an AC efficiently
- Right size matters: an AC that is too small runs flat out without cooling; one that is too big cools quickly but leaves the room damp.
- Inverter ACs slow down once the room is cool, which saves units in long running hours.
- Set 26°C: each degree lower adds noticeably to the bill.
- Cut heat gain: roof insulation, shaded windows and closed curtains on sunny sides reduce the load a lot on top floors.
See what the AC adds to your bill with the Appliance Running Cost Calculator, and whether solar can run it with the Solar System Calculator.
Features
Built for Pakistan
Assumes summer temperatures above 45°C and typical brick houses.
Heat factors
Extra load for top floors, sun, people and kitchens.
Power estimate
Typical power use of an inverter AC of that size.
When to use it
Buying an AC
Choose 1, 1.5 or 2 ton with confidence. See the monthly cost with the Appliance Running Cost Calculator.
Big lounges
Decide whether to use two units. See the full bill with the Electricity Bill Calculator.
Bedrooms
Avoid a unit that is too big or small. Run it on solar with the Solar System Calculator.
Shops and offices
Estimate cooling for small commercial rooms. Building? Plan with the Construction Cost Calculator.
Related Bills and Energy tasks
Frequently asked questions
What size AC do I need for a 12 × 14 room?
In Pakistan's climate, a 168 sq ft room usually needs a 1 ton AC, or 1.5 ton on a top floor or in a sunny room.
How many BTU is one ton?
One ton of cooling equals 12,000 BTU per hour.
Is a bigger AC better?
No. An oversized AC cools quickly but cycles on and off and controls humidity poorly. An undersized AC runs all the time.
Does an inverter AC save electricity?
Yes. Inverter ACs adjust speed and can use 30% to 50% less electricity than fixed-speed units.
How much electricity does a 1.5 ton inverter AC use?
Roughly 1 to 1.5 units an hour on a hot day, depending on temperature and settings.
What temperature should I set?
26°C is a good balance of comfort and lower bills.
Does insulation help?
Yes. Roof insulation, shading and sealing gaps reduce the AC size you need.
Does a 1.5 ton AC cool a big lounge?
A 1.5 ton AC suits about 180 to 220 sq ft in Pakistani summers. Larger lounges may need two units or a 2 ton AC.
Why does my AC not cool enough in June?
At 45°C and above, ACs lose capacity. Sun on walls and roofs adds heat, so an AC sized for mild weather struggles.
Is a DC inverter better than an AC inverter?
Both terms describe inverter technology. Compare the energy efficiency rating and real power use instead.
Does an old house need a bigger AC?
Older houses with thin roofs, single glazing and gaps around doors lose cool air faster, so they may need a slightly larger AC than a well-insulated modern house of the same size.
Results are estimates based on the official rates linked above. Confirm important figures with the issuing authority or a qualified adviser before you act on them.
Built and reviewed by Hamza Farooq, founder and lead developer
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