Calculating feet, inches, and inch fractions or adding length measurements can be done in a few simple steps.
Convert to a Common Unit of Measurement
If your measurement is in feet or contains feet, start by converting feet into inches by multiplying feet by 12. ie. 3 feet = 3*12 = 36 inches
Convert Inch Fractions to a Common Denominator
If you are working with fractions, the key will be to convert all of the inch fractions in the equation into the same format so the denominators(bottom numbers) are all the same. For example, 1/4” and 1/8” become 2/8” and 1/8” so they can be added together. For more help on converting fractions, check out the fraction lesson at math.com.
Add or Subtract Like Normal
The next step is to add or subtract the inch measurements just like any other numbers.
Determine the Number of Feet and Inches From the Answer
To get the final answer in feet and inches, start by taking the answer and dividing by 12. Take the whole number of the answer as the feet measurement, ie. 150 inches / 12 = 12.5 which will be 12 feet. Now take that number of feet and multiply by 12, ie. 12 becomes 144. Subtract 144 from 150 to get the number of inches, ie. 150 – 144 = 6 inches. The answer is now 12 feet 6 inches.
Reduce the Inch Fraction to the Lowest Denominator
Finally, convert any remaining fraction to a proper inch fraction. Inch fractions will always have an odd numerator(top number) and a denominator that is a power of 2(2,4,8,16,32,64). If the numerator of your fraction is even, divide both the numerator and denominator by two until the numerator is odd, ie. 4/8” becomes 2/4“, the numerator is still even so divide by 2 again to get 1/2“. If your fraction is 4/16“, divide by 2 to get 2/8” and again to get to 1/4“. If your numerator is odd like 3/8” or 5/16“, you’re done. See our reduce fractions calculator to learn more about reducing fractions.
Inch and Foot Calculator
There has to be a better way! If you’re still stuck or would like some help adding or subtracting length measurement’s, use our inch fractions calculator to quickly and easily calculate inch, feet, and metric measurements.