Carpenter Fraction Calculator: Add, Subtract, Multiply, Divide, and Scale Feet and Inches

Carpenter Fraction Calculator Sign

This carpenter tape measure calculator will add, subtract, multiply, and divide feet and inches and give the results in both decimal and tape measurement formats (rounded to your desired fraction of an inch).

Plus, if you're a model builder, and you want to scale up or down from kit dimensions, you can choose to multiply a tape measurement by a percentage (50% = half size, 200% = double size, etc.).

You can also use the scale option to convert inches to feet and inches (enter the inches and set the scale factor to 100%).

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Carpenter Fraction Calculator

Add, subtract, multiply, divide, and scale feet and inches, and see the results in decimal and tape measurement formats.

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Selected Data Record:

A Data Record is a set of calculator entries that are stored in your web browser's Local Storage. If a Data Record is currently selected in the "Data" tab, this line will list the name you gave to that data record. If no data record is selected, or you have no entries stored for this calculator, the line will display "None".

DataData recordData recordSelected data record: None
Feet and inches #1:

Feet and inches #1:

Enter the feet and inches for the first measurement. You can enter a decimal, fraction, or mixed number in the inches field. If entering a mixed number, leave exactly one space between the whole number and the fraction (1 3/8).

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Operation:

Operation:

Select the operation you wish to perform.

If you select x (times), the results will be reported in square inches (in2) and square feet (ft2).

If you select % (scale), the second feet and inches row will be replaced by a row for entering a percentage to scale the entered feet and inches.

Feet and inches #2:

Feet and inches:

Enter the feet and inches for the second measurement. You can enter a decimal, fraction, or mixed number in either field. If entering a mixed number, leave exactly one space between the whole number and the fraction (1 3/8).

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Tape measure rounding:

Rounding:

Select the fraction of an inch you would like the tape measurement result rounded to. The calculator will give both the rounded fractional inches and, if applicable, the reduced fractional inches (8/16 = 1/2).

Decimal result:

Decimal result:

This is the result of the operation in decimal format.

Tape measure result:

Fraction result:

This is the result of the operation in tape measure format, rounded to the selected fraction of an inch. If the numerator and denominator have a common factor, the fractional inch will be simplified (12/16 will be reduced to 3/4, as 12 and 16 have a greatest common denominator of 4).

If you would like to save the current entries to the secure online database, tap or click on the Data tab, select "New Data Record", give the data record a name, then tap or click the Save button. To save changes to previously saved entries, simply tap the Save button. Please select and "Clear" any data records you no longer need.

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Help and Tools

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How to Add and Subtract Feet and Inches

How to Add or Subtract Feet and Inches

Here are the steps to adding or subtracting feet and inch measurements.

Step #1: First feet and inch measurement: Convert the feet to inches and the inches to decimal inches, then add the feet and decimal inches to get the total decimal inches.

Step #2: Second feet and inch measurement: Convert the feet to inches and the inches to decimal inches, then add the feet and decimal inches to get the total decimal inches.

Step #3: Perform the operation on the two decimal inch totals from Steps #1 and #2.

Step #4: Convert the result in Step #3 back to feet and inches.

    4a: Divide the result from Step #3 by 12 (inches/foot) and round that result down to the nearest whole number. This becomes the "feet" portion of feet and inches result.

    4b: Multiply the feet portion of the measurement (result from 4a) by 12 and subtract that result from the total decimal inches to get the inches portion of the measurement.

This leaves you with the decimal feet and inches resulting from the addition or subtraction.

Step #5 (optional): Convert the decimal feet and inches to tape measure feet and inches.

    5a: The feet portion and whole-inch portion of the decimal feet and inches result remain the same for the tape measure result.

    5b: To convert the fractional portion of the decimal inches result to tape measure fractional inches, you multiply the fractional decimal inches by the denominator portion of the rounding value you selected (16 if rounding to 1/16), and then round that result to the nearest whole number which then becomes the numerator of the fractional inch (if the rounded result is 11, and rounding to nearest 16th, the fraction tape measure inch would be 11/16).

    5c: If the numerator and denominator from 5b have a common factor greater than 1, divide the numerator and denominator by their greatest common factor to get the reduced fractional inch.

The above 5 steps will leave you with the feet and inches result from adding or subtracting in both decimal and tape measure formats.

Example of How to Add Feet and Inches

Add 6 feet 5 1/4 inches to 3 feet 2 7/8 inches

Step #1: Convert 6' 5 1/4" to decimal inches.

    Convert 6' to decimal inches. Since 6 is already in decimal format, multiply 6 by 12 to get 72 decimal inches.

    Convert 5 1/4" to decimal inches. Convert the mixed number 5 1/4 to a decimal. To do that, we multiply the denominator 4 by the whole number 5 and then add that result (20) to the numerator 1 to get the new numerator 21. From there, we divide the new numerator by the denominator to get the decimal 5.25 (5 1/4 = 21/4 = 5.25).

    Add the feet decimal inches (72) to the inch decimal inches (5.25) to get 77.25 total decimal inches for 6' 5 1/4" .

Step #2: Convert 3' 2 7/8" to decimal inches.

    Convert 3' to decimal inches. Since 3 is already in decimal format, multiply 3 by 12 to get 36 decimal inches.

    Convert 2 7/8" to decimal inches. Convert the mixed number 2 7/8 to a decimal. To do that, we multiply the denominator 8 by the whole number 2 and then add that result (16) to the numerator 7 to get the new numerator 23. From there, we divide the new numerator by the denominator to get the decimal 2.875 (2 7/8 = 23/8 = 2.875).

    Add the feet decimal inches (36) to the inch decimal inches (2.875) to get 38.875 total decimal inches for 3' 2 7/8" .

Step #3: Perform the addition.

    Add the first total decimal inches (77.25) to the second total decimal inches (38.875) to get 116.125 total decimal inches.

Step #4: Convert the total decimal inches (116.125) to feet and inches.

    Divide 116.125 by 12 (inches) to get 9.6771 decimal feet.

    Round 9.6771 down to the nearest whole number to get the feet portion of the measurement (9).

    Multiply the feet portion of the measurement (9) by 12 and subtract that result (108) from the total decimal inches (116.125) to get the inches portion of the measurement (8.125).

    The decimal inches (116.125) have now been converted to 9' 8.125".

Step #5: Convert the decimal feet and inches (9' 8.125") to tape measure feet and inches.

    The feet portion and whole-inch portion of the decimal feet and inches result remain the same for the tape measure result (9 feet, 8 inches).

    To convert the fractional portion of the decimal feet and inches result (0.125) to tape measure fractional inches, you multiply the 0.125 by the denominator portion of the rounding value you selected (1/16), and then round that result (0.125 x 16 = 2) to the nearest whole number (2). This becomes the numerator of the fractional inch (2/16).

    However, since the numerator and denominator of (2/16) have a common factor greater than one (2), divide the numerator and denominator by 2 to get a reduced fractional inch of 1/8.

    The decimal feet and inches (9' 8.125") have now been converted to a 9' 8 1/8" tape measurement.

Example of How to Subtract Feet and Inches

Subtract 3 feet 2 7/8 inches from 6 feet 5 1/4 inches

Step #1: Convert 6' 5 1/4" to decimal inches.

    Convert 6' to decimal inches. Since 6 is already in decimal format, multiply 6 by 12 to get 72 decimal inches.

    Convert 5 1/4" to decimal inches. Convert the mixed number 5 1/4 to a decimal. To do that, we multiply the denominator 4 by the whole number 5 and then add that result (20) to the numerator 1 to get the new numerator 21. From there, we divide the new numerator by the denominator to get the decimal 5.25 (5 1/4 = 21/4 = 5.25).

    Add the feet decimal inches (72) to the inch decimal inches (5.25) to get 77.25 total decimal inches for 6' 5 1/4" .

Step #2: Convert 3' 2 7/8" to decimal inches.

    Convert 3' to decimal inches. Since 3 is already in decimal format, multiply 3 by 12 to get 36 decimal inches.

    Convert 2 7/8" to decimal inches. Convert the mixed number 2 7/8 to a decimal. To do that, we multiply the denominator 8 by the whole number 2 and then add that result (16) to the numerator 7 to get the new numerator 23. From there, we divide the new numerator by the denominator to get the decimal 2.875 (2 7/8 = 23/8 = 2.875).

    Add the feet decimal inches (36) to the inch decimal inches (2.875) to get 38.875 total decimal inches for 3' 2 7/8" .

Step #3: Perform the subtraction.

    Subtract the second total decimal inches (38.875) from the first total decimal inches (77.25) to get 38.375 total decimal inches.

Step #4: Convert the total decimal inches (38.375) to feet and inches.

    Divide 38.375 by 12 (inches) to get 3.1979 decimal feet.

    Round 3.1979 down to the nearest whole number to get the feet portion of the measurement (3).

    Multiply the feet portion of the measurement (3) by 12 and subtract that result (36) from the total decimal inches (38.375) to get the inches portion of the measurement (2.375).

    The decimal inches (38.375) have now been converted to 3' 2.375".

Step #5: Convert the decimal feet and inches (3' 2.375") to tape measure feet and inches.

    The feet portion and whole-inch portion of the decimal feet and inches result remain the same for the tape measure result (3 feet, 2 inches).

    To convert the fractional portion of the decimal feet and inches result (0.375) to tape measure fractional inches, you multiply the 0.375 by the denominator portion of the rounding value you selected (1/16), and then round that result (0.375 x 16 = 6) to the nearest whole number (6). This becomes the numerator of the fractional inch (6/16).

    However, since the numerator and denominator of (6/16) have a common factor greater than one (2), divide the numerator and denominator by 2 to get a reduced fractional inch of 3/8.

    The decimal feet and inches (3' 2.375") have now been converted to a 3' 2 3/8" tape measurement.

Adjust Calculator Width:

Move the slider to left and right to adjust the calculator width. Note that the Help and Tools panel will be hidden when the calculator is too wide to fit both on the screen. Moving the slider to the left will bring the instructions and tools panel back into view.

Also note that some calculators will reformat to accommodate the screen size as you make the calculator wider or narrower. If the calculator is narrow, columns of entry rows will be converted to a vertical entry form, whereas a wider calculator will display columns of entry rows, and the entry fields will be smaller in size ... since they will not need to be "thumb friendly".

Show/Hide Popup Keypads:

Select Show or Hide to show or hide the popup keypad icons located next to numeric entry fields. These are generally only needed for mobile devices that don't have decimal points in their numeric keypads. So if you are on a desktop, you may find the calculator to be more user-friendly and less cluttered without them.

Stick/Unstick Tools:

Select Stick or Unstick to stick or unstick the help and tools panel. Selecting "Stick" will keep the panel in view while scrolling the calculator vertically. If you find that annoying, select "Unstick" to keep the panel in a stationary position.

If the tools panel becomes "Unstuck" on its own, try clicking "Unstick" and then "Stick" to re-stick the panel.