How to Change Feet & Inches to Decimals

Calculating the amount of materials needed for a construction job can be a difficult task, particularly when measurements on remodeling plans are given in feet and inches. In addition, site plans and schematics may use different measurement schemes -- feet and inches or decimal feet -- and comparison between plans can be difficult. Instead of attempting to add or multiply fractions, you can simply convert each measurement to decimal feet for easy mathematics. For example, 7 feet 6 inches would convert to a decimal measurement of 7.5 feet.

As the old adage goes, measure twice and cut once.

Step 1

Determine the number of whole feet -- for example, a measurement of 6 feet 3 3/8 inches includes 6 whole feet. The number of whole feet will be given to the left of the decimal point -- in the example, this would be 6.00 feet.

Step 2

Convert fractions of inches to their decimal equivalents. For example, the measurement of 6 feet 3 3/8 inches includes a fraction of an inch -- 3/8. Divide the numerator by the denominator to find the decimal fraction of an inch -- that is, 3 divided by 8 equals 0.375 inches.

Step 3

Add whole inches and fractions of inches. For example, the measurement of 6 feet 3 3/8 inches includes 3 whole inches, and you have just calculated that 3/8 inches equals 0.375 inches, yielding a total of 3.375 inches.

Step 4

Convert inches to decimal feet by dividing the number of whole inches by the number of inches in a whole foot -- 12. For the example, 3.375 divided by 12 equals 0.28 feet.

Step 5

Add the decimal fraction of a foot to the number of whole feet. In the example, you would add 0.28 feet to 6.00 feet to find that 6 feet 3 3/8 inches equals 6.28 feet.