Feet and Inches Calculator

Use this feet and inches calculator to add or subtract measurements expressed in feet and inches. Results are shown in three formats simultaneously: feet and inches, total inches, and decimal feet. According to NIST, 1 foot equals exactly 0.3048 meters and 1 inch equals exactly 25.4 millimeters — fixed values used in all imperial unit calculations.

Working with feet and inches together is common in construction, carpentry, interior design, and height measurement. Unlike metric units, imperial measurements require handling two units simultaneously, which is where a dedicated calculator saves time and avoids errors.

How the Feet and Inches Calculator Works

Enter two measurements in feet and inches format. The calculator performs the selected operation (add or subtract) and returns results in three formats:

• Feet and inches — e.g., 11 ft 3 in
• Total inches — e.g., 135 in
• Decimal feet — e.g., 11.25 ft

Adding example: 5 ft 9 in + 5 ft 6 in = 11 ft 3 in (135 inches total)

Subtracting example: 10 ft 4 in − 3 ft 8 in = 6 ft 8 in (80 inches total)

Feet and Inches Addition — Step by Step

To manually add feet and inches:

1. Add the inches together
2. If total inches is 12 or more, divide by 12 — quotient becomes extra feet, remainder stays as inches
3. Add all feet together including any carried over from step 2

Example: 4 ft 10 in + 3 ft 7 in

Step 1: 10 + 7 = 17 inches.

Step 2: 17 ÷ 12 = 1 ft, remainder 5 in.

Step 3: 4 + 3 + 1 = 8 ft, plus 5 in = 8 ft 5 in.

Feet and Inches Subtraction — Step by Step

To manually subtract feet and inches:

1. If the second inches value is larger than the first, borrow 1 foot (12 inches) from the feet column
2. Subtract the inches
3. Subtract the feet

Example: 7 ft 3 in − 2 ft 9 in

Step 1: 3 in is less than 9 in — borrow 1 ft, giving 6 ft 15 in.

Step 2: 15 − 9 = 6 in.

Step 3: 6 − 2 = 4 ft. Result: 4 ft 6 in.

Common Feet and Inches Conversions

Where This Calculator Is Used

Construction and Framing: Adding wall lengths, beam spans, and floor dimensions measured in feet and inches. Totalling multiple measurements for accurate material estimates prevents costly over-ordering or shortfalls.

Carpentry and Woodworking: Calculating board lengths, cutting dimensions, and fitting measurements where plans are drawn in feet and inches. Standard construction measuring tapes often come in 5 km reels (approximately 16,404 feet) — tradespeople regularly cross-reference metric tape lengths with imperial blueprint dimensions.

Interior Design and Renovation: Adding room dimensions, subtracting door or window openings from wall lengths, and planning furniture layouts in feet and inches.

Height Calculations: Adding or comparing heights expressed in feet and inches — common in sports, medical records, and clothing sizing. Average US male height of 5 ft 9 in equals 69 total inches or 5.75 decimal feet.

Fabric and Sewing: Calculating total fabric needed when individual pieces are measured in feet and inches. Each foot contains 12 inches, so a 3 ft 6 in piece equals 42 total inches of material.

Limitations of This Calculator

• This calculator handles whole inches only — for fractional inches (¼", ⅛"), use a dedicated fractions calculator
• Multiplication and division of feet-and-inches measurements (e.g., area) require a separate area calculator
• Results assume the international foot (0.3048 m). The US survey foot (0.3048006 m) differs at the 6th decimal place — irrelevant for construction but relevant in geodetic surveying

For related length conversions, try our yards to inches converter or cm to feet converter.