How to Measure a Room for BTUs

Measure BTUs for a Heater

• 1

  Measure the length of the room from the middle of one wall to the opposite wall. Record the measurement in feet. For example, if the length is 12 feet 6 inches, record 12.5 feet.

• 2

  Measure the width of the room from the middle of the adjacent wall to the middle of the opposite wall. Record the measurement in feet.

• 3

  Measure the height of the room from the middle of the ceiling to the middle of the floor. Record the measurement in feet.

• 4

  Multiply the length, width and height of the room to determine its volume. For example, if the length is 12.5 feet, the width 10.8 feet and height 10.2 feet, the volume is 1,377 cubic feet (12.5 x 10.8 x 10.2).

• 5

  Multiply the volume of the room by 5 if your room has one to two windows and average insulation. Multiply the volume of the room by 6 if your room has two or more windows or poor insulation. Multiply the volume by 7 if the room faces north. For example, if your room has 3 windows, poor insulation and faces north, multiply the volume by 7 to get (1377 x 7) 9,639 BTUs. For this room, a 10,000 to 12,000 BTU heater will be suitable.

Measure BTUs for an Air Conditioner

• 6

  Measure the length of the room from the middle of one wall to the next. Record the measurement in feet. For example, if the length is 12 feet 6 inches, record 12.5 feet.

• 7

  Measure the width of the room from the middle of the adjacent wall to the middle of the opposite wall. Record the measurement in feet.

• 8

  Multiply the length and width of the room to determine its area. For example, if the length is 12.5 feet and the width 10.8 feet, the area is 135 square feet (12.5 x 10.8).

• 9

  Multiply the area of the room by 25 to determine the number of BTUs you need to cool the room. Add 1,000 for every window and 400 for each occupant in the room. Add 4,000 for air conditioners located in the kitchen. Add 2,000 for poor insulation. For example, if the room has an area of 135 square feet, poor insulation, 2 windows and 2 people that frequent it regularly, it needs 8,175 BTUs to heat it (135 x 25 + 2,000 + 2,000 + 800). For this room, a 9,000 to 11,000 BTU air conditioner will be suitable.