Feet and Inches to Decimal Feet Converter

How it works

Every length is first turned into total inches. Feet, inches and a fraction become 12 × feet + inches + numerator ÷ denominator; decimal feet are multiplied by 12; centimetres are divided by 2.54, since an inch is exactly 25.4 mm. From total inches everything else follows: decimal feet are inches ÷ 12, metres are inches × 0.0254, and centimetres are inches × 2.54.

Feet and inches are read back by taking the whole feet, then the inches left over. The headline rounds those leftover inches to the nearest sixteenth, the finest mark on a typical tape, and carries a full 16/16 into the next inch and 12 inches into the next foot, so 180 cm, which is 70.866 in, reads 5 ft 10 7/8 in. The decimal figures below it are exact and not rounded to a mark.

Decimal feet are what plans, surveys and construction estimates use (12.5 ft rather than 12 ft 6 in), while tapes read in feet and inches; this converter moves between the two. The centimetre mode is the usual height conversion: 180 cm is 5 ft 10.87 in.

Formula

total inches  = 12 × feet + inches + numerator ÷ denominator      (feet-inches mode)
              = 12 × decimal feet                                 (decimal feet mode)
              = centimetres ÷ 2.54                                (centimetre mode)
decimal feet  = total inches ÷ 12
feet, inches  = floor(total inches ÷ 12), remainder
metres        = total inches × 0.0254;  centimetres = total inches × 2.54
nearest 1/16  = round(total inches × 16) ÷ 16, fraction reduced

Example

5 ft 10 in, the default, is 5 × 12 + 10 = 70 in, which is 70 ÷ 12 = 5.8333 ft, 70 × 0.0254 = 1.778 m and 177.8 cm. With a 1/2 in fraction it becomes 70.5 in = 5.875 ft = 179.07 cm.

180 cm is 180 ÷ 2.54 = 70.8661 in: 5 ft and 10.87 in, or 5 ft 10 7/8 in to the nearest sixteenth, and 5.9055 ft. 12.5 ft is 150 in = 12 ft 6 in = 3.81 m.

Assumptions and limitations

• 1 ft = 12 in and 1 in = 2.54 cm, both exact definitions; metric values come from the shared length table.
• The feet-and-inches headline is rounded to the nearest 1/16 in (so at most 1/32 in from the true length), with exact halves rounding up. The numeric outputs are not rounded to a mark.
• Lengths are non-negative. Inches of 12 or more and fractions of a full inch or more are accepted and carried into feet and inches.
• Adding or subtracting two feet-and-inch lengths is not covered here; convert each to inches, combine, then convert back.

Frequently asked questions