BuildMeasureWorking with Feet, Inches, and Fractions
Mixed feet, inches, and fractions are easy to misread during a project. A dependable method is to convert everything to one small unit, perform the arithmetic, and then convert the answer back.
Convert feet to inches
Multiply feet by 12 and add the remaining inches. For example, 5 feet 7 inches equals 67 inches. Keep the fractional inch attached to that total.
Use a common denominator
When fractions differ, convert them to a shared denominator. One quarter is 4/16 and three eighths is 6/16. This makes addition and subtraction direct.
Borrow one foot during subtraction
If the inches in the first measurement are smaller, borrow one foot as 12 inches. For example, subtracting 2 ft 10 in from 4 ft 3 in becomes 3 ft 15 in minus 2 ft 10 in, which equals 1 ft 5 in.
Keep precision appropriate
More decimal places do not make an uncertain measurement more accurate. Choose a practical fraction for the tool and task, then round once at the end. Record whether a dimension is finished, rough, or a target clearance.
Check the result physically
Arithmetic supports layout; it does not replace a test fit. Confirm critical dimensions on the actual assembly and account for blade position, joinery, and measuring from a consistent reference face.