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Air Conditioner BTU Calculator & Guide

Getting the right size air conditioner matters. Too small, and it won’t cool properly. Too big, you may be wasting energy. Our BTU calculator makes it easy to find a unit that suits your room—and helps you stay energy smart too.

BTU stands for British Thermal Unit. It measures how much heat an air con can remove from a room in an hour. The higher the BTU, the more powerful the cooling. But more isn’t always better - matching the BTU to your room size is key for comfort and efficiency.

Use our calculator below to get a tailored BTU recommendation in seconds.

Air Conditioner Calculator

Use our simple calculator to find the right BTU rating for your space. Just enter your room size, number of people, and heat-producing devices.

What are the room dimensions?

How many people and heat sources are in the room?

What is a BTU?

A BTU (British Thermal Unit) measures how much heat an air con can remove from a room per hour. The bigger the number, the more powerful the cooling.

Small rooms might need around 7,000 BTU, while large commercial spaces can go well over 25,000 BTU.

What Affects the BTU You Need?

Several factors can impact your BTU needs:

  • Room size: Larger rooms need more cooling power.
  • Ceiling height: Higher ceilings mean more air to cool.
  • Sunlight: Very sunny rooms? Add around 10% more BTUs.
  • Shade: Shaded space? You may be able to reduce BTUs by 10%.
  • People: Add 600 BTUs per person after the first two.
  • Kitchens: Add 4,000 BTUs due to heat from appliances.
  • Insulation: Poor insulation? You’ll likely need more power.

Air Conditioner Sizing FAQs

  • What does BTU stand for?
    • BTU stands for British Thermal Unit. It's a measure of how much heat an air con can remove in one hour.
  • What happens if my AC is too big (too many BTUs)?
    • It cools too fast and doesn’t remove enough humidity. That can make the space feel cold and damp, and cause wear from turning on and off too often.
  • What happens if my AC is too small (too few BTUs)?
    • It’ll run constantly and struggle to cool the room, using more energy and potentially wearing out quicker.
  • Do I need different BTUs for different room types?
    • Yes. Kitchens need more due to appliance heat. Other rooms follow standard sizing but may need adjusting based on sun, size, and use.
  • Is this calculator 100% accurate?
    • It’s a great estimate, but things like local climate, insulation, and window quality can affect results. Use it as a guide and check product details for best results.

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