Add, subtract, multiply, and divide measurements in feet and inches
Enter feet and inches in the top and bottom fields. Pick an operation (+, -, ×, ÷) from the dropdown.
Built with for builders and DIYers
Founder & CEO, Toolraxy
Faiq Ur Rahman is a web designer, digital product developer, and founder of Toolraxy, a growing platform of web-based calculators and utility tools. He specializes in building structured, user-friendly tools focused on health, finance, productivity, and everyday problem-solving.
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Working with measurements in feet and inches is a daily reality for builders, carpenters, DIY enthusiasts, and anyone involved in construction or home improvement. A feet and inches calculator simplifies these tasks by allowing you to perform arithmetic operations, addition, subtraction, multiplication, and division directly on measurements that include fractions. This tool is designed for anyone who regularly works with imperial measurements and needs a fast, accurate way to combine lengths, calculate material requirements, or adjust dimensions. By entering values like “5+1/2” or “3/4” and selecting an operation, you can instantly see the result in both feet/inches and decimal formats, saving time and reducing costly measurement errors.
Enter Value 1: Type your first measurement in the top field. You can use mixed numbers (e.g., 5+1/2), simple fractions (e.g., 3/4), or whole numbers (e.g., 7).
Select an Operator: Click one of the four buttons: + (add), − (subtract), × (multiply), or ÷ (divide).
Enter Value 2: Type your second measurement in the bottom field using the same format.
Choose Precision: Select the desired fraction precision from the dropdown (e.g., 1/8, 1/16, 1/64).
View Your Result: The calculator instantly displays the result in feet and inches, fraction form, decimal feet, decimal inches, and total inches.
This tool converts all inputs to a common unit (inches), performs the selected arithmetic operation, and then converts the result back to a human-readable feet and inches format with your chosen precision.
Core Logic:
The calculator operates in three stages: parsing, computation, and formatting.
The primary formulas and logic are as follows:
Input Parsing:
Mixed numbers: 5+1/2 is interpreted as 5 whole units plus 1/2 unit.
Simple fractions: 3/4 is interpreted as 0.75 units.
Whole numbers: 7 is interpreted as 7 units.
All inputs are converted to decimal inches for calculation. The tool assumes the input is in inches, so 5+1/2 means 5.5 inches.
Arithmetic Operations:
Addition: Result = Value 1 + Value 2
Subtraction: Result = Value 1 − Value 2
Multiplication: Result = Value 1 × Value 2
Division: Result = Value 1 ÷ Value 2 (if Value 2 is zero, an error is displayed)
Result Formatting:
The total inches are split into feet and inches: Feet = Floor(Total Inches ÷ 12), Inches = Total Inches % 12.
The remaining fractional part of an inch is rounded to the nearest fraction based on the selected precision (e.g., 1/8 precision rounds to the nearest eighth).
The tool also displays the result as a simplified fraction (e.g., 0.75 becomes 3/4), decimal feet (Total Inches ÷ 12), and decimal inches.
Let’s walk through a practical scenario for a woodworker.
Scenario: You have two pieces of wood—one measuring 5 feet 6 inches (5+1/2), and another measuring 3 feet 3 inches (3+1/4). You need to find their combined length.
Steps and Results:
Enter Value 1: Type 5+1/2 into the first field.
Select Operator: Click the + button.
Enter Value 2: Type 3+1/4 into the second field.
Choose Precision: Keep the default 1/8.
Interpretation: The result section now displays:
Result: 8 ft 0.75 in (or 8 ft 3/4 in depending on formatting)
Decimal Feet: 8.7292 ft
Decimal Inches: 104.7500 in
Operation: 5.50 in + 3.25 in = 8 ft 0.75 in
Takeaway: The calculator has added the two lengths together (5.5 inches + 3.25 inches = 8.75 inches) and formatted the result as 8 feet and 3/4 inch. This confirms the combined length of the two boards.
How accurate is this feet and inches calculator?
The calculator is highly accurate. It performs all arithmetic in decimal inches and then rounds the result to your selected precision (e.g., 1/8 inch). The rounding is done mathematically, ensuring the closest correct fraction is displayed.
Can I enter negative measurements?
The input fields accept text, so you can type a leading minus sign (e.g., -5+1/2). The parser handles this correctly, and subtraction operations with negative values will produce accurate results.
What causes the “Division by zero!” message?
This message appears if you select the division (÷) operator and enter 0 or 0/1 in the second value field. Division by zero is mathematically undefined, so the tool displays an error instead of a result.
Is this tool safe and private to use?
Yes, it is completely safe and private. The calculator is a client-side application, meaning all calculations are performed locally in your web browser. The measurements you enter are never transmitted, processed, or stored on any server.
What is the difference between 1/8 and 1/16 precision?
Precision refers to the smallest fraction of an inch used in the final rounded result. 1/8 precision rounds to the nearest eighth of an inch (e.g., 0.125, 0.25, 0.375). 1/16 precision rounds to the nearest sixteenth (e.g., 0.0625, 0.125, 0.1875). Higher precision gives a finer, more exact result.
Can I use decimal inches instead of fractions?
Yes, the calculator accepts decimal inputs in the value fields. For example, entering 5.5 is interpreted as 5.5 inches. You can also mix formats, such as 5+0.5 for 5.5 inches.
Does the tool convert to metric units?
This specific tool is designed for imperial measurements (feet and inches). For metric conversions, you would need a different tool or unit converter.
Why is my result shown as “0 in” for a very small fraction?
If the final result is less than the selected precision (e.g., less than 1/8 inch when precision is set to 1/8), the tool rounds down to zero. To see the small fraction, increase the precision to 1/32 or 1/64.
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