Feet and Inches Calculator – Add and Subtract Fraction and Decimal Inches, Feet, CM, and MM

Add or subtract inches (both decimal and fraction), feet, centimeters and millimeters. Enter equations just like you would write it on paper, eg. 4′ 3 7/8″ + 5cm. Get results in inches (fraction and decimal), feet, centimeters, and millimeters – all measurements are displayed in imperial and metric.

Calculating inches, inch fractions, feet and centimeters

Inches, Feet, Fraction, Centimeters, and Millimeters Results

0"

Imperial Units

0 Inches (fraction)
0 Inches
0 Feet

Metric Units

0 Millimeters
0 Centimeters
0 Meters

How to Add, Subtract, Multiply, or Divide Feet, Inches, and Metric Length Measurements

Add, subtract, multiply, and divide as many imperial and metric length values as you want, using normal math equations just like you would write.
Enter inch, foot, centimeter, or millimeters, using symbols, abbreviations, or names.

Get final length measurements in feet, inches, inches in fraction, and decimal form, millimeters, and centimeters. Results will be rounded to the nearest inch fraction.

Converting to Decimal Inches

The first thing to do when adding, subtraction, or doing other math with inches, feet, and other measurements is to convert all of the measurements into a common unit of measurement.

Start by converting inch fractions into decimal, then convert feet, centimeters, and millimeters to inches.

To convert inch fractions to decimal by dividing the bottom half of the fraction by the bottom half on a calculator. If there is a whole number, add it to the decimal value after converting. Our inch fraction calculator can also find the decimal value for an inch fraction
For example:
3/8 = 3 ÷ 8 = .375 inches

Convert feet to inches by multiplying the number of feet by 12, since there are 12 inches in a foot. Use our feet to inches conversion calculator to easily convert.
For example:
3 feet = 3 × 12 = 36 inches

Convert centimeters to inches by dividing the number of centimeters by 2.54, as there are 2.54 centimeters in an inch. You can also use our centimeters to inches conversion calculator.
For example:
5 centimeters = 5 ÷ 2.54 = 1.97 inches

Convert millimeters to inches by dividing the number of centimeters by 25.4. You can also use our millimeters to inches conversion calculator.
For example:
50 millimeters = 50 ÷ 25.4 = 1.97 inches

Adding or Subtracting Inches and Feet

With all measurements in an inch decimal form, add or subtract all measurements as you normally would, using a calculator as needed. The final result will be in inch decimal form and will need to be converted to the desired output measurement.

Multiplying or Dividing Inches and Feet

It is also possible to multiply and divide inches, which can be done by multiplying or dividing the decimal value by a number of your choice. For example, if your inch value is 1.25 and you need to multiply by 2, simply multiply using 1.25 × 2 = 2.5.

Adding Common Inch Fractions

Table showing the sum of common inch fractions. Add a fraction from the top heading and first column, the sum is where they intersect.
+ 1/8″ + 1/4″ + 3/8″ + 1/2″ + 5/8″ + 3/4″ + 7/8″ + 1″
1/8″ 1/4″ 3/8″ 1/2″ 5/8″ 3/4″ 7/8″ 1″ 1 1/8″
1/4″ 3/8″ 1/2″ 5/8″ 3/4″ 7/8″ 1″ 1 1/8″ 1 1/4″
3/8″ 1/2″ 5/8″ 3/4″ 7/8″ 1″ 1 1/8″ 1 1/4″ 1 3/8″
1/2″ 5/8″ 3/4″ 7/8″ 1″ 1 1/8″ 1 1/4″ 1 3/8″ 1 1/2″
5/8″ 3/4″ 7/8″ 1″ 1 1/8″ 1 1/4″ 1 3/8″ 1 1/2″ 1 5/8″
3/4″ 7/8″ 1″ 1 1/8″ 1 1/4″ 1 3/8″ 1 1/2″ 1 5/8″ 1 3/4″
7/8″ 1″ 1 1/8″ 1 1/4″ 1 3/8″ 1 1/2″ 1 5/8″ 1 3/4″ 1 7/8″
1″ 1 1/8″ 1 1/4″ 1 3/8″ 1 1/2″ 1 5/8″ 1 3/4″ 1 7/8″ 2″

Subtracting Common Inch Fractions

Table showing the difference of common inch fractions. Subtract a fraction from the top heading from first column, the difference is where they intersect.
− 1/8″ − 1/4″ − 3/8″ − 1/2″ − 5/8″ − 3/4″ − 7/8″ − 1″
1/8″ 0″ -1/8″ -1/4″ -3/8″ -1/2″ -5/8″ -3/4″ -7/8″
1/4″ 1/8″ 0″ -1/8″ -1/4″ -3/8″ -1/2″ -5/8″ -3/4″
3/8″ 1/4″ 1/8″ 0″ -1/8″ -1/4″ -3/8″ -1/2″ -5/8″
1/2″ 3/8″ 1/4″ 1/8″ 0″ -1/8″ -1/4″ -3/8″ -1/2″
5/8″ 1/2″ 3/8″ 1/4″ 1/8″ 0″ -1/8″ -1/4″ -3/8″
3/4″ 5/8″ 1/2″ 3/8″ 1/4″ 1/8″ 0″ -1/8″ -1/4″
7/8″ 3/4″ 5/8″ 1/2″ 3/8″ 1/4″ 1/8″ 0″ -1/8″
1″ 7/8″ 3/4″ 5/8″ 1/2″ 3/8″ 1/4″ 1/8″ 0″

Multiplying Common Inch Fractions

Table showing the multiplication of common inch fractions. Multiply the fraction in the first column by the value in the top heading, the result is where they intersect.
× 2 × 3 × 4 × 5 × 6 × 7 × 8
1/8″ 1/4″ 3/8″ 1/2″ 5/8″ 3/4″ 7/8″ 1″
1/4″ 1/2″ 3/4″ 1″ 1 1/4″ 1 1/2″ 1 3/4″ 2″
3/8″ 3/4″ 1 1/8″ 1 1/2″ 1 7/8″ 2 1/4″ 2 5/8″ 3″
1/2″ 1″ 1 1/2″ 2″ 2 1/2″ 3″ 3 1/2″ 4″
5/8″ 1 1/4″ 1 7/8″ 2 1/2″ 3 1/8″ 3 3/4″ 4 3/8″ 5″
3/4″ 1 1/2″ 2 1/4″ 3″ 3 3/4″ 4 1/2″ 5 1/4″ 6″
7/8″ 1 3/4″ 2 5/8″ 3 1/2″ 4 3/8″ 5 1/4″ 6 1/8″ 7″
1″ 2″ 3″ 4″ 5″ 6″ 7″ 8″

Dividing Common Inch Fractions

Table showing the division of common inch fractions. Divide the fraction in the first column by the value in the top heading, the result is where they intersect.
÷ 2 ÷ 3 ÷ 4 ÷ 5 ÷ 6 ÷ 7 ÷ 8
1/4″ 1/8″ 5/64″ 1/16″ 3/64″ 1/32″ 1/32″ 1/64″
1/2″ 1/4″ 11/64″ 1/8″ 7/64″ 5/64″ 1/16″ 1/16″
3/4″ 3/8″ 1/4″ 3/16″ 5/32″ 1/8″ 7/64″ 3/32″
1″ 1/2″ 21/64″ 1/4″ 13/64″ 11/64″ 9/64″ 1/8″

Inch Fraction and Decimal Equivalents

Find common inch fractions and equivalent decimal values using a fraction chart.


Chart showing decimal values for every inch fraction from 1/64" - 1"

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