How to Calculate Ac

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BTU Air Conditioning Calculator

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Calculation Summary

Required Cooling Capacity:

BTUs per Hour

Recommended AC Size in Tons:

function calculateBTU() { var length = parseFloat(document.getElementById('roomLength').value); var width = parseFloat(document.getElementById('roomWidth').value); var occupants = parseInt(document.getElementById('occupants').value); var sun = document.getElementById('sunlight').value; var isKitchen = document.getElementById('isKitchen').checked; if (isNaN(length) || isNaN(width) || length <= 0 || width 2) { baseBTU += (occupants – 2) * 600; } // Adjust for kitchen if (isKitchen) { baseBTU += 4000; } var tons = baseBTU / 12000; document.getElementById('btuOutput').innerText = Math.round(baseBTU).toLocaleString(); document.getElementById('tonOutput').innerText = tons.toFixed(2) + " Tons"; document.getElementById('acResult').style.display = "block"; }

How to Calculate AC Capacity (BTU Guide)

Choosing the right size air conditioner is crucial for both comfort and energy efficiency. An undersized unit will run constantly without cooling the room, while an oversized unit will turn on and off too frequently (short-cycling), leading to poor dehumidification and higher electricity bills.

The Basic BTU Formula

The standard rule of thumb for residential cooling is 20 BTU per square foot of living space. However, real-world conditions require adjustments based on how the room is used and its exposure to the elements.

  • Room Area: Length × Width.
  • Sunlight: If the room is heavily shaded, reduce capacity by 10%. If the room is very sunny, increase it by 10%.
  • Occupancy: If more than two people regularly occupy the room, add 600 BTUs for each additional person.
  • Kitchens: If the unit is for a kitchen, add an additional 4,000 BTUs to account for cooking heat.

What is a "Ton" of Air Conditioning?

In HVAC terms, a "ton" does not refer to the weight of the machine. It refers to the cooling capacity. One ton of cooling is equal to 12,000 BTUs per hour. For example, a 24,000 BTU unit is a 2-ton air conditioner.

Example Calculation

Imagine a living room that is 20 feet long and 20 feet wide (400 sq. ft.).

  1. Base Calculation: 400 sq. ft. × 20 BTU = 8,000 BTUs.
  2. Sunny Adjustment: If it has large south-facing windows, add 10% (+800 BTUs) = 8,800 BTUs.
  3. People Adjustment: If 4 people live there, add 1,200 BTUs (600 × 2 extra people) = 10,000 BTUs.
  4. Total Requirement: You would look for a unit with at least 10,000 BTU capacity.

Why Accuracy Matters

Calculating the correct AC size prevents "short-cycling." Air conditioners don't just cool the air; they remove moisture. If a unit is too large, it cools the room so fast that it shuts off before it can remove the humidity, leaving you with a cold but "clammy" environment. Using this calculator helps ensure you find the perfect balance for your specific room dimensions.

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