F&I

Feet and Inches Calculator

Quickly add, subtract, multiply, or divide feet and inches with this easy-to-use measurement calculator.

Result

11 ft 9.3 in

calculator-display

Something went wrong with your calculation.

Feet and Inches Calculator

The imperial system of feet and inches remains a cornerstone in construction, carpentry, interior design, and everyday tasks across the United States and other parts of the world. However, performing accurate arithmetic with imperial units can become tedious, especially when dealing with mixed numbers or fractional values. That's where our Feet and Inches Calculator becomes invaluable. This tool simplifies calculations involving feet and inches—whether you're adding, subtracting, multiplying, or dividing—and saves you from costly mistakes and time-consuming manual work.

Manual Imperial Units Calculations

Imperial unit calculations differ from metric system operations due to the absence of a base-10 structure. In the imperial system, 1 foot equals 12 inches, so any operation involving these measurements must account for conversion factors. Manual calculations often require converting mixed numbers to a single unit before computing and then converting back to the desired form. While calculators can expedite this process, understanding the manual steps provides deeper insight and accuracy for complex projects.

Conversion Method

A common approach is converting all values to one consistent unit—either feet or inches—before performing operations. Afterward, the result can be reconverted into feet and inches as needed. This method simplifies the math and ensures consistency throughout the process.

Adding Feet and Inches

To add 2 feet 8½ inches and 2 feet 5¾ inches, convert them to inches first:

  • 2' 8½" = (2 × 12) + 8½ = 32½ inches
  • 2' 5¾" = (2 × 12) + 5¾ = 29¾ inches
  • Sum = 32½ + 29¾ = 62¼ inches
  • Convert to feet: 62¼ ÷ 12 = 5' 2¼"

Subtracting Feet and Inches

For example, subtract 3 feet 9½ inches from 5 feet 2¾ inches:

  • Convert to inches: 62¾ – 45½ = 17¼ inches = 1' 5¼"

Multiplying Feet and Inches

When multiplying 5 feet 2¾ inches by 3 feet 9½ inches, convert to inches:

  • 62.75 in × 45.5 in = 2855.125 in²
  • Convert to ft²: 2855.125 ÷ 144 = 19.827 ft²

Dividing Feet and Inches

To divide 5' 2¾" by 3' 9½":

  • 62.75 ÷ 45.5 = 1.3791 (unitless ratio)

Calculation Without Unit Conversion

You can also calculate directly in feet and inches without converting. Just perform operations from the smallest unit (inches) to the largest (feet), borrowing or carrying over as needed.

Addition Example:

  • ¾" + ½" = 1¼" → carry over 1"
  • 2" + 9" + 1" = 12¼" → carry over 1'
  • 5' + 3' + 1' = 9'
  • Final result = 9' ¼"

Subtraction Example:

  • ¾" – ½" = ¼"
  • Borrowing needed: 2" becomes 14" – 9" = 5"
  • 5' becomes 4' – 3' = 1'
  • Final result = 1' 5¼"

Measurements Based on Human Body in History

Before standardization, body parts were commonly used for measurement. These units made practical sense in daily life and often varied by person or region.

Finger

Roughly ¾ inch, a finger was widely used in ancient civilizations. It was a standard subdivision of the cubit and is still used informally (e.g., a "finger" of whiskey).

Palm

Typically 3 inches or 75 mm. The palm was divided into 4 fingers and was used in Egypt, Israel, and medieval Europe.

Hand

Standardized at 4 inches and still used today to measure the height of horses. Originated from the width of a human hand.

Cubit

The cubit is the distance from the elbow to the tip of the middle finger, ranging from 44 to 52 cm historically. Used in ancient Egypt and biblical texts.

Shaftment

A shaftment is 6 inches (half a foot) and was defined by the width of the fist and extended thumb. Common in medieval England.

Foot

Now defined as 0.3048 meters, the foot originated from the average length of a human foot. Still widely used in the U.S. and U.K. for height and construction.

Ell

Derived from the forearm's length, the ell varied from 27 to 54 inches in Europe. Used for tailoring and textiles. Became obsolete after the Weights and Measures Act of 1824.

Fathom

Used for measuring water depth, a fathom equals 6 feet. Still common in maritime navigation and fishing industries.

Smoot

Initially a humorous unit, the smoot was created in 1958 at MIT, defined as the height of Oliver R. Smoot (5'7"). It became an actual measurement on the Harvard Bridge in Boston and remains a novelty unit of length.

Why Use the Feet and Inches Calculator?

Our Feet and Inches Calculator is designed to take the stress out of complex arithmetic involving imperial units. Whether you're doing home renovations, working in architecture, or simply calculating your height, the calculator allows you to:

  • Effortlessly switch between feet and inches
  • Perform operations with mixed numbers and fractions
  • Get instant, accurate results for all mathematical operations
  • Avoid common errors from manual calculations

This tool is an essential companion for contractors, students, engineers, and DIYers alike. Try our Feet and Inches Calculator now and simplify your next measurement task with precision and ease!