Feet and Inches Calculator

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Calculate mixed measurements, rectangular area and perimeter, or complete unit-aware expressions.

First length
Second length
Length
Width

Results

Enter measurements above, then calculate to see the result and unit equivalents.

Measurement diagram

Calculation
Only need to convert a measurement? Use the Decimal Feet Converter
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This calculator handles arithmetic that a simple converter intentionally does not. Use structured fields for dependable everyday work, or switch to Expression when a calculation is easier to write in one line. Length arithmetic stays in length units. Rectangle calculations keep square area separate from linear perimeter. Expression mode applies the same rule automatically, so multiplying two lengths produces an area and dividing one length by another produces a ratio.

About This Tool

The Feet and Inches Calculator combines four common length operations, a rectangle calculator, and a unit-aware expression field. It accepts decimal values and common fractions, normalizes inches across foot boundaries, and presents one coherent result in customary and metric units. Its scope is measurement arithmetic. For a quick conversion between decimal feet and a tape-measure reading, the dedicated Decimal Feet Converter remains the simpler choice.

How to Use

  1. Choose Length, Rectangle, or Expression mode
  2. Enter measurements and choose fraction and decimal precision
  3. Calculate and review the result type and unit equivalents

Methodology

All length inputs are normalized to inches before arithmetic. The exact international relationships 1 foot = 12 inches, 1 inch = 0.0254 meter, and 1 foot = 0.3048 meter provide the customary-to-metric conversions. For a rectangle, area equals length multiplied by width and perimeter equals twice the sum of length and width. Area therefore uses square units, while perimeter remains a length. Fraction rounding is applied only when formatting the feet-and-inches display.

Sources: NIST — SI conversion factors · NIST — Area and perimeter

Understanding Your Results

A length result leads with feet, inches, and your selected fraction increment, followed by decimal feet, total inches, meters, centimeters, and millimeters. Negative results are retained so subtraction can show direction or difference. An area result leads with square feet and includes other square units. The perimeter remains a mixed length. A unitless expression result is labeled as a ratio rather than a length or area.

Sources

Practical Examples

Example 1: Add 8 ft 7 3/8 in and 2 ft 4 1/2 in. The result is 10 ft 11 7/8 in, or 10.9896 decimal feet. Example 2: A rectangle 8 ft by 10 ft has an area of 80 ft² and a perimeter of 36 ft. The area is square measure; the perimeter is linear measure.

Measurement Tips

• Match the fraction setting to the smallest mark you actually measured; extra displayed precision cannot improve the source measurement. • Use the factor field only for a plain number, such as a quantity or scale. Use Rectangle when both values are lengths. • Keep units on every measured value in an expression. Parentheses make the intended order clear. • Check whether the required answer is a length, area, or ratio before copying it into a plan or estimate.

All calculations are performed locally in your browser. No data is sent to any server.

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Frequently Asked Questions
What is the Feet and Inches Calculator for?
It performs arithmetic with mixed feet-and-inches measurements. You can add or subtract two lengths, scale one length by a number, calculate a rectangle, or enter a complete measurement expression. Results are shown as feet, inches, fractions, decimals, and metric equivalents.
How do I enter fractional inches?
Enter a whole number, decimal, fraction, or mixed number in an inches field. For example, 7, 7.375, 3/8, 7 3/8, and 7-3/8 are accepted. In expression mode, include a unit such as in, inch, inches, or the inch symbol.
What does multiplying or dividing a length mean?
In Length mode, multiplication and division use a unitless numeric factor. For example, 2 ft 6 in multiplied by 3 equals 7 ft 6 in. To multiply two lengths and obtain an area, use Rectangle mode or enter a unit-aware expression.
Why are area and perimeter in a separate mode?
Length and area describe different quantities. Adding lengths produces another length, while multiplying two lengths produces square units. The separate Rectangle mode makes that change explicit and returns both the rectangular area and its perimeter without mixing the two meanings.
Which expressions can I enter?
Expression mode accepts addition, subtraction, multiplication, division, and parentheses. Units include feet, inches, meters, centimeters, and millimeters. Compatible quantities can be added, two lengths can be multiplied into area, and dividing one length by another returns a unitless ratio.
How does fractional rounding work?
Choose the smallest displayed inch increment from 1/2 through 1/64. The feet-and-inches result is rounded to the nearest selected increment and reduced to its simplest fraction. Decimal and metric outputs use the separate decimal-places setting, so the display choice does not change the calculation.
How is this different from the Decimal Feet Converter?
This calculator solves arithmetic, rectangle, and expression tasks. The Decimal Feet Converter is focused on quick, bidirectional conversion between decimal feet and feet, inches, and fractions, and it includes a dedicated reference table. Use the converter when no arithmetic is needed.
Are my measurements private?
Yes. Calculations run in your browser, and measurement values are not submitted to a server. If you choose Copy Link with Settings, the current values are placed in the link itself so that you can deliberately share or reopen that setup.