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Kalcufy

Feet to Inches Converter

Convert feet to inches — including decimal feet to sixteenths, the exact 25.4 mm inch, and the survey foot the US retired in 2023.

Conversion table

LengthIn Inches
0.56 in
112 in
1.518 in
224 in
2.530 in
336 in
448 in
560 in
672 in
784 in
896 in
9108 in
10120 in
12144 in
15180 in

📊 Decimal Feet to Fractions

  • 0.0625 ft3/4 in
  • 0.125 ft1½ in
  • 0.25 ft3 in
  • 0.375 ft4½ in
  • 0.5 ft6 in
  • 0.75 ft9 in

Reading a Tape Measure Like a Trade

  • US construction never uses decimal inches. A tape is divided into halves, quarters, eighths and sixteenths — so 4.5 in is written 4½ in.
  • To turn a decimal inch into a fraction, multiply by 16 and put the result over 16: 0.375 × 16 = 6, so 6/16 = 3/8 in.
  • 5'11" means 5 feet 11 inches, which is 71 in. It does NOT mean 5.11 feet — that would be 5 ft 1.3 in.
  • A 55-inch TV measures 55 in on the diagonal. In 16:9 that is only 47.9 in wide, which is why it fits a smaller shelf than people expect.

The Inch Has Been Exactly 25.4 Millimeters Since 1959

The foot and the inch are now defined through the metric system, not the other way round. The International Yard and Pound Agreement of 1959 fixed the yard at exactly 0.9144 meters, which makes the foot exactly 0.3048 meters and the inch exactly 25.4 millimeters. Those are definitions with no error bar. Before 1959 there were two competing inches: the American one worked out to about 25.4000508 mm and the British imperial one to about 25.399977 mm. On a tape measure the difference is invisible, but on a survey baseline or a machine tolerance it was real enough that both countries agreed to abandon their own standards and adopt a single number.

Decimal Feet Are Not How Anyone Builds

Multiplying feet by twelve is the easy half. The part that trips people up is what to do with the decimal: a spreadsheet that says 5.7 ft is useless on a job site, because no tape measure has tenths. Convert it in two steps. First take the whole feet — 5 — and set them aside. Then multiply the decimal by 12 to get inches: 0.7 × 12 = 8.4 in. Finally turn the leftover 0.4 into a fraction by multiplying by 16, giving 6.4 sixteenths, which rounds to 6/16 or 3/8. So 5.7 ft reads as 5 ft 8⅜ in on a tape, and that is the number a carpenter can actually cut to.

The Other Foot, Retired in 2023

  • The US survey foot was defined as 1200/3937 meters, which works out to 0.30480060960 m — about two parts per million longer than the international foot.
  • Two parts per million sounds like nothing, but it drifts 3.2 mm over a mile and 32 cm over a hundred miles. On a state plane coordinate grid that is a real position error.
  • It survived because US land surveys, property boundaries and state coordinate systems were all built on it and could not be silently redefined.
  • NIST and NOAA formally retired the survey foot on 31 December 2022; from 2023 only the international foot is official in the United States.
  • Legacy survey data still carries the old foot, so mixing an old plat with a modern GPS reading without checking the unit is a genuine hazard.
  • None of this affects the inch: 12 survey inches make a survey foot, so the ratio you use on this page is unchanged.

Where the Catalogue Is in Inches and Your Number Is in Feet

  • Screens: televisions and monitors are sold by diagonal inches. A 55 in 16:9 panel is 47.9 in wide and 27.0 in tall.
  • Bicycle wheels: 26 in, 27.5 in and 29 in are the standard sizes, and none of them is quoted in feet anywhere.
  • Pipe: nominal pipe size is given in inches — ½ in, ¾ in, 1 in — even though the actual outside diameter does not match the name.
  • Lumber: a stud sold as 8 ft is usually cut to 92⅝ in so that with plates it makes a 97⅛ in wall for an 8 ft ceiling.
  • Human height: 5 ft 11 in is 71 in, or 180.3 cm. Sports rosters and ID documents use feet and inches, medical records use centimeters.
  • Rims and tyres: a 17 in wheel is 17 inches at the bead seat, never expressed in feet.

Worked Examples

Decimals turned into something you can measure

Turning 5.7 ft into a tape measurement

  1. Keep the whole feet: 5 ft
  2. Decimal to inches: 0.7 × 12 = 8.4 in
  3. Leftover to sixteenths: 0.4 × 16 = 6.4 ≈ 6/16 = 3/8 in

5.7 ft = 5 ft 8⅜ in = 68.4 in

A door opening of 6 ft 8 in

  1. Feet to inches: 6 × 12 = 72 in
  2. Add the inches: 72 + 8 = 80 in
  3. In decimal feet that is 80 ÷ 12 = 6.667 ft

6 ft 8 in = 80 in = 203.2 cm

Frequently Asked Questions

How many inches are in 5 feet 7?

67 inches. Multiply the feet by 12 and add the inches: 5 × 12 = 60, plus 7 gives 67 in, which is 170.2 cm. Note that 5 ft 7 in is not 5.7 ft — that would be 68.4 in.

Why is a 55-inch TV not 55 inches wide?

Because televisions are measured on the diagonal. A 16:9 panel with a 55 in diagonal is 47.9 in wide and 27.0 in tall. That is why a set often fits a shelf people assumed was too narrow, or overhangs one they assumed was wide enough.

What is the US survey foot and why was it retired?

It was a slightly longer foot — 1200/3937 m, about two parts per million above the international foot — kept alive for land surveying because property boundaries and state coordinate systems were built on it. NIST and NOAA retired it on 31 December 2022, so from 2023 the United States uses only the international foot.

How do I convert a decimal foot to inches and a fraction?

Multiply the decimal part by 12 to get inches, then multiply whatever is left over by 16 to get sixteenths. For 0.375 ft: 0.375 × 12 = 4.5 in, and 0.5 × 16 = 8, so 8/16 = ½. The answer reads 4½ in.

Is the inch the same everywhere?

Yes, since 1959. The international inch is exactly 25.4 mm, adopted by the US, UK, Canada, Australia, New Zealand and South Africa. Before that agreement the American and British inches differed in the fifth decimal place.

Why do American builders use fractions instead of decimals?

Because a tape measure is physically divided by halving — half, quarter, eighth, sixteenth — rather than by tens. Reading 3/8 off a tape takes a glance; reading 0.375 requires converting first. The fractions match the tool, so they stayed.

How many inches is an 8-foot stud?

96 inches nominally, but a precut stud sold for an 8 ft wall is usually 92⅝ in. The missing 3⅜ in is taken up by the bottom plate and the two top plates, giving a finished wall just over 97 in.

Sources