Feet and Inches Calculator – Add or Subtract Feet, Inches, and Fractions

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.

Feet, Inches, and Metric Measurements:

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Inches, Feet, Fraction, Centimeters, and Millimeters Results

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Imperial Units

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Metric Units

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On this page:

• How to Add or Subtract Feet & Inches
• Step One: Convert Feet and Inches to Decimal
• Step Two: Add or Subtract the Converted Values
• How to Multiply or Divide Feet & Inches
• Step One: Convert Feet and Inches to Decimal
• Step Two: Multiply or Divide
• Inch Fraction and Decimal Equivalents

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How to Add or Subtract Feet & Inches

Adding or subtracting feet and inches might seem difficult, but it’s actually really easy if you follow a few simple steps. It’s even easier to add or subtract length values using a calculator like the one above, but if you want to learn how to do it yourself, follow these easy steps.

Step One: Convert Feet and Inches to Decimal

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.

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.

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.

Try our other length conversion calculators to convert other units to decimal inches.

Step Two: Add or Subtract the Converted Values

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.

To express the sum or difference value in feet, simply multiply by 12.

The following charts simplify the process of adding and subtracting fractional inch values together and might be faster than using a calculator.

Common Inch Fraction Additions

Common Inch Fraction Subtractions

How to Multiply or Divide Feet & Inches

The steps to multiply or divide feet and inches are similar to the steps for adding and subtracting above.

Step One: Convert Feet and Inches to Decimal

The first step in multiplying or dividing is to convert the length measurements to a decimal value. If the length measurements are in feet and inches, it might be easiest to convert to inches.

Step Two: Multiply or Divide

With the length value converted to a decimal, it’s now possible to multiply or divide just like you would with any decimal number. For example, if your inch value is 1.25 and you need to multiply by 2, simply multiply using 1.25 × 2 = 2.5.

The following charts make multiplying or dividing fractional inch values much easier.

Common Inch Fraction Multiplications

Common Inch Fraction Divisions

Inch Fraction and Decimal Equivalents

Sometimes a chart makes things easier: find common inch fractions and equivalent decimal values using this one.