Window Air Conditioner Size Calculator

Calculate the right BTU capacity for your window air conditioner based on room dimensions. Get instant recommendations for optimal cooling efficiency.

Calculate Required BTU

How to Calculate Air Conditioner Size

Determining the right size air conditioner for your room is crucial for optimal cooling efficiency and comfort. This guide explains the calculation method used by HVAC professionals to select the appropriate BTU rating.

Air Conditioner Size Formula

The basic formula for calculating required BTU capacity is:

\[ BTU = A \times 20 \]

Where:

  • BTU = British Thermal Units needed for cooling
  • A = Room area in square feet (length × width)
  • 20 = Standard BTU requirement per square foot

To calculate room area:

\[ A = L \times W \]

Where:

  • L = Room length in feet
  • W = Room width in feet

Calculation Steps

  1. Measure room length and width in feet
  2. Calculate room area by multiplying length × width
  3. Multiply area by 20 BTU/sq ft to get required capacity
  4. Round up to nearest standard AC unit size

Example Calculation

Problem:

Calculate the required AC size for a room with:

  • Length = 15 feet
  • Width = 12 feet

Solution:

  1. Calculate room area:
    \[ A = L \times W = 15 \text{ ft} \times 12 \text{ ft} = 180 \text{ sq ft} \]
  2. Calculate required BTU:
    \[ BTU = 180 \text{ sq ft} \times 20 \text{ BTU/sq ft} = 3,600 \text{ BTU} \]
  3. Round to standard size: 4,000 BTU unit recommended

Room Cooling Visualization

Width (W) Length (L) Cooling Coverage