Feet Inches Calculator

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feet inches calculator
Add Lengths (+)Subtract Lengths (-)Convert Inches to Feet/InchesConvert Decimal Feet to Feet/Inches
Result:
function updateFields(){var type=document.getElementById('calc_type').value;var r2=document.getElementById('row2');var ft1=document.getElementById('ft1');var in1=document.getElementById('in1′);if(type==='conv_in'){r2.style.display='none';ft1.style.display='none';in1.placeholder='Total Inches';in1.style.width='100%';}else if(type==='conv_ft'){r2.style.display='none';in1.style.display='none';ft1.placeholder='Decimal Feet';ft1.style.width='100%';}else{r2.style.display='table-row';ft1.style.display='inline-block';in1.style.display='inline-block';ft1.placeholder='ft';in1.placeholder='in';ft1.style.width='50%';in1.style.width='50%';}}function calculateResult(){var type=document.getElementById('calc_type').value;var f1=parseFloat(document.getElementById('ft1').value)||0;var i1=parseFloat(document.getElementById('in1').value)||0;var f2=parseFloat(document.getElementById('ft2').value)||0;var i2=parseFloat(document.getElementById('in2').value)||0;var showDec=document.getElementById('show_decimal').checked;var totalInches1=(f1*12)+i1;var totalInches2=(f2*12)+i2;var resultInches=0;var mainText="";var subText="";if(type==='add'){resultInches=totalInches1+totalInches2;}else if(type==='sub'){resultInches=totalInches1-totalInches2;}else if(type==='conv_in'){resultInches=i1;}else if(type==='conv_ft'){resultInches=f1*12;}var absInches=Math.abs(resultInches);var resFt=Math.floor(absInches/12);var resIn=Math.round((absInches%12)*1000)/1000;if(resultInches<0){mainText="- ";}mainText+=resFt+" ft "+resIn+" in";if(showDec){subText="Total Inches: "+resultInches.toFixed(2)+"\"
Total Decimal Feet: "+(resultInches/12).toFixed(4)+" ft";}document.getElementById('mainResult').innerHTML=mainText;document.getElementById('subResult').innerHTML=subText;document.getElementById('answer').style.display='block';}

How to Use the Feet Inches Calculator

The feet inches calculator is a specialized tool designed to simplify architectural, construction, and DIY measurements. Because the United States customary system uses a base-12 ratio for length (12 inches = 1 foot), performing simple arithmetic like addition or subtraction can become complex when "carrying over" inches into feet. This calculator automates that process.

Whether you are calculating the height of a doorway, the total length of baseboards needed for a room, or converting rough measurements from a blueprint, this tool provides instant results in both standard and decimal formats.

Add/Subtract Lengths
Enter the feet and inches for two different measurements. The calculator will combine or find the difference between them, automatically adjusting the feet when inches exceed 11 or drop below 0.
Convert Inches to Feet/Inches
Enter a large number of inches (e.g., 74) to see the equivalent in standard feet and inches format (6 ft 2 in).
Convert Decimal Feet
Useful for engineering plans that often use decimal feet (e.g., 10.5 ft). The tool converts this to the more practical 10 ft 6 in.

How It Works: The Math Behind the Measurements

The logic used by the feet inches calculator follows a three-step process to ensure mathematical precision:

Total Inches = (Feet × 12) + Inches

  • Step 1: Normalize to Inches. All inputs are first converted into the smallest unit (inches). For example, 5′ 2″ becomes 62 inches.
  • Step 2: Perform Operation. The addition, subtraction, or conversion is performed on the total number of inches.
  • Step 3: Re-convert to Imperial format. The result is divided by 12 using floor division to find the feet, and the remainder (modulus) becomes the inches.

Feet and Inches Calculation Examples

Example 1: Adding Wall Lengths
Suppose you have two walls measuring 8 feet 9 inches and 4 feet 7 inches. You need to find the total length.

Step-by-step solution:

  1. Convert Wall 1: (8 × 12) + 9 = 105 inches
  2. Convert Wall 2: (4 × 12) + 7 = 55 inches
  3. Add: 105 + 55 = 160 inches
  4. Divide by 12: 160 / 12 = 13 with a remainder of 4
  5. Result: 13 ft 4 in

Example 2: Subtracting Clearance
You have a space of 6 feet 2 inches and want to install a cabinet that is 2 feet 10 inches wide. How much space is left?

  1. Convert Space: (6 × 12) + 2 = 74 inches
  2. Convert Cabinet: (2 × 12) + 10 = 34 inches
  3. Subtract: 74 – 34 = 40 inches
  4. Divide by 12: 40 / 12 = 3 with a remainder of 4
  5. Result: 3 ft 4 in

Common Questions

How many inches are in a foot?

There are exactly 12 inches in one foot. This base-12 system is standard in the United States and the United Kingdom for height and construction measurements.

What is 5'7″ in total inches?

To find the total inches, multiply the feet by 12 and add the remaining inches: (5 × 12) + 7 = 60 + 7 = 67 inches. Using a feet inches calculator makes this calculation instantaneous for larger or more complex numbers.

How do you convert decimal feet to inches?

To convert decimal feet to inches, multiply the decimal part by 12. For example, in 6.25 feet, take 0.25 and multiply by 12 to get 3 inches. The result is 6 feet 3 inches.

Why is it better to use a calculator for this?

Human error is common when adding imperial measurements because we are conditioned to work in base-10 (decimals). People often mistakenly add 5'10" and 1'5″ to get 6'15", forgetting to convert those 15 inches into 1'3″, which would result in 7'3″. A calculator eliminates this specific type of error.

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