Feet and Inches Calculator

Quick Answer

Last updated: 10 November 2026 ·How we calculate this: converting to inches (12 in = 1 ft) and back

How This Feet and Inches Calculator Works

Enter the first length in feet and inches, choose an operation, then enter the second length or a number. Inches can include fractions, such as 7 1/2 or 9 3/8. The calculator turns every length into inches, does the sum, and turns the answer back into feet and inches rounded to the nearest 1/16 inch (or the fraction you choose). It also gives total inches, decimal feet, yards, meters and centimeters.

How to Use the Feet and Inches Calculator

1. Enter the first length in feet and inches (fractions allowed).
2. Choose add, subtract, multiply, divide, or divide by a length.
3. Enter the second length or the number.
4. Choose how finely to round fractions.
5. Press Calculate to see feet and inches, decimal feet and metric.

Feet and Inches Formulas

• To inches: feet × 12 + inches
• Back to feet and inches: feet = whole part of (inches ÷ 12); inches = the remainder
• Decimal feet: inches ÷ 12
• Metric: inches × 2.54 = centimeters (exact)
• Fractions: round the remainder to the nearest 1/16, 1/8 or 1/4 inch and simplify

Key Terms

• Foot: a length of 12 inches, exactly 0.3048 m.
• Inch: a length of exactly 2.54 cm.
• Fractional inch: part of an inch written as a fraction, such as 3/8 or 5/16.
• Decimal feet: a length in feet written with decimals, such as 7.25 ft.
• Kerf: the width of material a saw blade removes in a cut.

Worked Example

You have a 12 ft board and cut off 4′ 8 3/8″. How much is left?

• 12 ft = 144 inches; 4′ 8 3/8″ = 48 + 8.375 = 56.375 inches
• 144 − 56.375 = 87.625 inches
• 87.625 ÷ 12 = 7 feet with 3.625 inches left over
• The piece left is 7′ 3 5/8″, not counting the width of the saw cut.

Real-Life Examples

• Adding walls: 5′ 7 1/2″ + 3′ 9 1/4″ = 9′ 4 3/4″.
• Cutting a board: 12′ − 4′ 8 3/8″ = 7′ 3 5/8″.
• Repeating a part: six shelves of 2′ 4 1/2″ need 14′ 3″ of board.
• Pieces from a board: an 8 ft board gives 3 pieces of 2′ 6″, with 6″ left over.

Feet and Inches vs Decimal Feet

• Feet and inches (5′ 6″) are used on tape measures, plans and in building.
• Decimal feet (5.5 ft) are used in surveying, estimating and spreadsheets.
• Converting: 6 inches is 0.5 ft, 3 inches is 0.25 ft and 1 inch is about 0.0833 ft.

Inches as Decimal Feet

Tips for Measuring

Tape measures in the US mark inches in sixteenths, with longer lines for 1/2, 1/4 and 1/8. When cutting several pieces from one board, remember the saw blade removes about 1/8 inch each cut (the kerf), so add it to each piece. For framing, many builders work in total inches and convert at the end, which avoids mistakes carrying feet and inches.

Everyday Uses

Feet and inches come up whenever you measure in a home or workshop: fitting a sofa through a doorway, centering a picture on a wall, laying out cabinets, cutting trim or baseboard, spacing fence posts, or checking whether a fridge fits a gap. Adding up room lengths for flooring or crown molding, and halving a wall length to find its center, are quick with this calculator.

Common Mistakes to Avoid

• Carrying 10 instead of 12. 16 inches is 1 foot 4 inches, not 1 foot 6 inches.
• Writing 5.6 ft for 5′ 6″. 5′ 6″ is 5.5 ft.
• Forgetting the saw kerf when cutting several pieces from one board.
• Mixing fractions and decimals in one number, such as 7.5 1/2.
• Rounding too early. Round only the final answer.

Frequently Asked Questions

References & Sources