Home, energy & building
AC BTU Calculator
Choose the right size window unit, mini-split or portable AC. Enter the room area and ceiling height, then adjust for sunlight, number of people, kitchen use and your climate. The calculator suggests a standard BTU size and tonnage.
How to use the AC BTU Calculator
- Enter room area in square feet.
- Enter ceiling height.
- Choose sun exposure and climate.
- Enter people and tick kitchen if needed.
Formula
Example
A 350 sq ft living room with normal sun and 2 people needs about 7,000 BTU - an 8,000 BTU unit.
Why size matters
- Too big: short cycles, clammy air, higher wear
- Too small: runs constantly and cannot keep up on hot days
Tons, BTU and Pakistani AC sizes
In Pakistan, air conditioners are usually sold by ton: 1 ton is 12,000 BTU per hour, 1.5 ton is 18,000 and 2 ton is 24,000. A typical 12 × 14 ft bedroom often needs a 1 ton unit, and a large lounge or a room under a hot roof may need 1.5 to 2 tons.
Things that need a bigger AC
- Top-floor rooms under a sunny roof
- West-facing windows that get afternoon sun
- Very hot cities such as Multan, Sukkur or Jacobabad
- Kitchens and rooms with many people or computers
Save electricity
Inverter ACs use much less power at part load. Setting the thermostat to 26°C instead of 18°C can cut running cost sharply, and sealing gaps around doors and windows helps any AC. Use the UPS and solar calculators if you plan backup power.
Related free tools
Frequently asked questions
How many BTU is 1 ton?
12,000 BTU per hour.
Is this for central air?
For whole-home systems, get a Manual J load calculation from an HVAC pro.
Does insulation matter?
Yes - poor insulation or many windows need a bigger unit.
BTU to watts?
1 BTU per hour ≈ 0.293 W of cooling.
Is a bigger AC always better?
No. An oversized AC cools quickly but switches on and off often and leaves the room damp.
How do I convert BTU to tons?
Divide BTU per hour by 12,000.
Results are estimates for planning. Your inputs stay in your browser and are not sent to Soft2Cloud.
Last updated: November 2026