Feet and Inches Calculator

Article — Feet and Inches Calculator

Feet and inches: convert, add, and subtract imperial measurements

A measurement of 70 inches equals 5 feet 10 inches, since 70 divided by 12 leaves a remainder of 10. The same length is 5.83 in decimal feet and 177.80 centimeters. The feet-and-inches calculator on this page converts in either direction, adds two measurements with automatic carry, and subtracts when one length is shorter than the other.

The math is base-12 inside the inches column and base-10 once you reach decimal feet or centimeters. The two constants are exact, fixed by the 1959 International Yard and Pound Agreement: 1 inch is 2.54 centimeters and 1 foot is 12 inches. Every calculation on this page rolls those two factors.

What are feet and inches?

The foot is a length unit going back to ancient Rome, Greece, and Egypt, where it tracked the length of a typical adult male foot. Modern English-speaking measurement settled on a 12-inch foot in medieval times. The word "inch" comes from the Latin uncia, meaning "one twelfth", which is exactly the ratio between an inch and a foot.

Today only three countries officially use the foot as a primary length unit: the United States, Liberia, and Myanmar. In practice, the United Kingdom, Canada, Ireland, India, and Australia all keep feet and inches alive for personal height and a handful of household measurements. The U.S. construction industry, U.S. real estate, and U.S. aviation all use feet and inches as the default.

Inches to feet and inches

To convert total inches into feet and inches, divide by 12 and use the remainder. The formula is short:

The reverse direction is just as fast. Multiply the feet by 12 and add the inches: 5 ft 10 in becomes 60 + 10 = 70 inches. The calculator runs both directions and shows all five equivalents (feet+inches, decimal feet, total inches, centimeters, meters) for every input.

Decimal feet vs feet and inches

Surveyors, civil engineers, and many drafting programs report lengths in decimal feet rather than feet and inches. The two are not interchangeable; one extra step is needed to translate. The whole-number part stays as feet; the decimal part times 12 gives the inches.

• 3.25 ft = 3 ft 3 in (since 0.25 × 12 = 3)
• 5.5 ft = 5 ft 6 in (since 0.5 × 12 = 6)
• 5.83 ft = 5 ft 9.96 in (since 0.83 × 12 = 9.96)
• 8.25 ft = 8 ft 3 in
• 10.75 ft = 10 ft 9 in
• 12.5 ft = 12 ft 6 in

A surveyor reading 5.6 ft on a tape is not reading 5 feet 6 inches. The conversion is 5 ft + (0.6 × 12) in = 5 ft 7.2 in. Treating 5.6 ft as 5 ft 6 in is the most common construction-math error, and it cascades quickly across a job that involves dozens of measurements.

Adding feet and inches

To add two ft+in measurements, convert each to total inches, add, and translate back. The arithmetic has a carry step at every 12, the same way base-60 minutes carry into hours. The calculator on this page handles the carry automatically.

Subtraction can produce a negative result, which the calculator shows with a minus sign. In construction contexts, a negative ft+in usually means a cut that runs short, while in real-estate floor plans it often means a measurement reversed. Always double-check which length is which before treating a negative result as a real subtraction.

Feet and inches to centimeters

For metric output, multiply the total inches by 2.54. The factor is exact, defined since 1959 by international treaty, so the only rounding involved is in the input measurement itself.

• 5 ft 0 in = 60 in = 152.40 cm
• 5 ft 4 in = 64 in = 162.56 cm
• 5 ft 8 in = 68 in = 172.72 cm
• 5 ft 10 in = 70 in = 177.80 cm
• 6 ft 0 in = 72 in = 182.88 cm
• 6 ft 2 in = 74 in = 187.96 cm
• 6 ft 4 in = 76 in = 193.04 cm

For a quick mental estimate, multiply feet by 30 and inches by 2.5, then add. The approximation undershoots by about 1.6 percent, which is fine for converting heights between an American and a European reading. 5 ft 10 in by the shortcut is 150 + 25 = 175 cm; the exact value is 177.80 cm.

Feet and inches for height

The most common application of feet and inches today is human height. American passports, driver's licenses, and medical charts all use feet and inches, even though the CDC and the National Health and Nutrition Examination Survey collect the underlying data in centimeters.

Median adult male height in the United States is 5 ft 9 in (175 cm), and median adult female height is 5 ft 4 in (162 cm), per CDC NHANES 2015-2018. The tallest verified human was Robert Wadlow at 8 ft 11.1 in (272 cm), measured by Guinness in 1940. The tallest verified woman was Zeng Jinlian at 8 ft 1.75 in (248 cm).

Fractional inches in construction

Carpenters, plumbers, and machinists almost never use decimal inches. The construction trade reads to the nearest 1/16 inch, with finer work going to 1/32 or 1/64. The conversion is straightforward: multiply the decimal part by 16 (or 32, or 64) and round to the nearest whole, then reduce the fraction by the greatest common divisor.

5 ft 9.96 in rounded to the nearest 1/16 becomes 5 ft 9 15/16 in (since 0.96 × 16 = 15.36, rounded to 15). The 0.04-inch rounding error is roughly 1 mm, which is below the resolution of most construction tape measures. For higher-precision work, the inches-to-fraction calculator on this site handles the rounding plus shows the absolute error.

Common feet and inches mistakes

• Treating 5.6 ft as 5 ft 6 in — decimal feet uses hundredths of a foot. 5.6 ft = 5 ft 7.2 in.
• Forgetting the carry — 5 ft 14 in is really 6 ft 2 in. The calculator rolls it for you, but pencil-and-paper math sometimes leaves the 14 as is.
• Mixing the prime marks — 5'10" means 5 feet 10 inches. The single mark is feet, the double mark is inches.
• U.S. survey foot in modern work — the survey foot was retired in 2023. All federal length work now uses the international foot of exactly 0.3048 m.
• Decimal inches in carpentry — trades work in 1/16, 1/32, or 1/64 inch. Convert before measuring on a tape.
• Rounding too aggressively — rounding 70.5 in to 5 ft 10 in throws away half an inch (1.27 cm), which matters for cabinetry and clothing.