Height Converter

A converter built on an exact number

Every height conversion on this page rests on a single fact: one inch is exactly 2.54 centimeters. It is not an approximation that happens to be close. It is a legal definition, and it means that converting between metric and imperial heights never loses accuracy until you choose to round.

The definition is younger than many people realize. NIST records that in 1958 a conference of English-speaking nations agreed to unify their standards of length and mass in metric terms. Before that, the American yard and the British imperial yard differed slightly. The compromise shortened the American yard and lengthened the imperial one so both equal exactly 0.9144 meters. The United States announced the new values in Federal Register Notice 59-5442 on June 30, 1959, effective the next day. Divide 0.9144 m by the 36 inches in a yard and you get 0.0254 m, or 25.4 mm, per inch.

One leftover from the old system lasted surprisingly long. The US survey foot, defined as 1200/3937 of a meter (about 0.3048006 m), was kept for land surveying. It differs from the international foot by roughly two parts per million, irrelevant for a person's height but significant over hundreds of miles of map. NIST retired it for all uses after December 31, 2022.

Why Americans still say "five foot nine"

Feet and inches have been defined by the meter in the United States far longer than most people assume. The Metric Act of 1866 made metric units legal in trade, the US was one of the original signatories of the 1875 Treaty of the Metre, and the Mendenhall Order of 1893 adopted the international metric prototypes as the country's fundamental standards of length and mass. Since then, the yard, foot and inch have officially been fractions of a meter, with the 1959 agreement simply tidying the exact ratio.

Everyday usage never followed. The Metric Conversion Act of 1975 set up a voluntary changeover and a US Metric Board, which was disbanded in 1982, and a 1988 trade law named metric the preferred system for trade and commerce without requiring it elsewhere. The result is a split that shows up whenever height is discussed. American doctors usually talk to patients in feet and inches, while clinics often record height in centimeters, and body mass index is always expressed in kilograms per square meter even when it is calculated from pounds and inches. The UK, Canada and Ireland show a similar mix, with official forms and health records largely metric and conversation often imperial. That is exactly the gap a height converter fills.

The formulas the converter uses

The tool keeps one value internally, height in centimeters, and derives everything else from it. That way every box on the screen always agrees with every other box.

A foot is 12 × 2.54 = 30.48 cm exactly, which is where the decimal-feet shortcut comes from. Decimal feet are rarely used for human height, but they appear in some engineering and medical records, so the distinction matters, as the section on notation below explains.

Handling the edge where inches round up to 12

A subtle bug affects many simple converters. Take 182.8 cm. That is 71.97 inches, or 5 feet and 11.97 inches. Rounded to the nearest whole inch, the remainder becomes 12, and a careless converter prints the impossible 5′12″. This site's conversion code carries that extra 12 inches into the feet column, so 182.8 cm displays correctly as 6′0″. The same carry applies when rounding to one decimal place.

Reading a free-typed height

The "type any height" box accepts the formats people actually use, and it interprets them with a few explicit rules:

• Feet and inches with symbols or words: 5′11″, 5'11, 5 ft 11 in, 5 feet 11 and 5 11 all mean 5 feet 11 inches.
• Units at the end: 180 cm, 1.8 m, 1800 mm and 71 in are read in the unit given.
• Bare numbers: below 3 is treated as meters (1.75), from 3 to just under 9 as feet, and anything larger as centimeters (175).
• The "5.11" convention: a bare number such as 5.11 or 5.9 is read as feet and inches, 5′11″ or 5′9″, because that is overwhelmingly what people mean when they type it. Only when the part after the decimal point exceeds 11, as in 5.75, is it treated as decimal feet.

That last rule deserves a warning, because decimal feet and feet-plus-inches look alike but differ. Five and a half feet is 5′6″ (167.64 cm). Five feet five inches is 165.1 cm. If you really mean decimal feet, add the unit: typing 5.5 ft returns 167.64 cm, while 5.5 alone returns 165.1 cm.

Worked examples at familiar heights

Going the other way, a few exact values are worth remembering: 5′0″ is 152.4 cm, 5′4″ is 162.56 cm, 5′7″ is 170.18 cm, 5′10″ is 177.8 cm, 6′0″ is 182.88 cm and 7′0″ is 213.36 cm. The cm-to-feet and feet-to-cm charts list every value in between, and individual pages such as 180 cm in feet and 5′10″ in cm show the arithmetic and place the height next to average adults.

Mental shortcuts and where they go wrong

When no converter is at hand, people reach for round numbers. The two most popular shortcuts are "divide centimeters by 2.5 to get inches" and "30 centimeters is a foot." They are convenient, and they are both the same approximation, because 2.5 × 12 = 30. The trouble is that both overstate height by about 1.6%, which at adult heights is roughly an inch.

An inch is precisely the kind of difference people care about when comparing heights, so the shortcut is fine for estimating the size of a bookshelf and poor for stating a person's height. A better mental method starts from a known anchor: 5′0″ is 152.4 cm, and every additional inch adds 2.54 cm. Ten inches therefore add 25.4 cm, so 5′10″ is 152.4 + 25.4 = 177.8 cm. Going the other way, 6′0″ is 182.88 cm, and each centimeter is about 0.39 inches. With those two anchors and a little arithmetic you can stay within a few millimeters.

Other common slips

• Rounding before converting. Rounding 175.26 cm to 175 cm and converting back gives 5′8.9″, not 5′9″. Convert the most precise value you have and round once, at the end.
• Writing inches without feet. "68 inches" is 5′8″ (172.72 cm), not 6′8″. When in doubt, the "total inches" box shows the plain inch value.
• Mixing up meters and centimeters. Typing 1.75 into a centimeter field produces a height of under 2 cm. The free-text box avoids this by reading small bare numbers as meters.
• Treating 5.11 as a decimal. In decimal feet, 5.11 is 155.8 cm; in everyday writing it means 5′11″, or 180.3 cm, a difference of almost 25 cm. The converter assumes the everyday meaning unless you add "ft."

Why the same height can be written two ways

Rounding is the most common reason two sources disagree about the same person's height. A height of 177 cm is 5′9.69″. Truncate it and you get 5′9″; round it and you get 5′10″. Both are "correct" depending on the convention, and they differ by an inch. This matters most for heights that sit near a half-inch boundary, which is why this converter always shows one decimal place before you decide how to round.

There is also a well-documented human tendency to round up. A 2024 systematic review in the journal Nutrients found that self-reported and measured heights generally agree well, but that men tend to overreport their height. A 2018 meta-analysis of 21 studies covering 18,749 women of reproductive age found self-reported height averaged 0.36 cm more than measured height. The effect is small on average but helps explain why so many people describe themselves as exactly 6 feet. When a conversion matters, for a medical form or a uniform, convert a measured value rather than a remembered one.

Your height is not a fixed number

Precise conversion makes it tempting to quote a height to two decimal places, but bodies are less precise than arithmetic. Spinal discs compress under load during the day and recover overnight. A study in Clinical Biomechanics that measured adults 24 times over a full day found a trough-to-peak change in stature of about 1.8 cm, with the largest drop in the first hour after getting up. A study of schoolchildren in Archives of Disease in Childhood found most of the daily loss occurred during the morning, with little change after about six hours awake.

So a person who measures 175.3 cm on rising may measure about 173.5 cm by evening, roughly 5′9″ versus 5′8.3″. Converting either value is exact; choosing which value represents "your height" is the real decision. Measuring at a consistent time, ideally in the morning, gives the most comparable results.

How to measure your height for an accurate conversion

1. Remove shoes and anything on top of your head, and stand on a hard floor rather than carpet.
2. Stand with heels together and heels, buttocks, shoulder blades and the back of your head against a flat wall.
3. Look straight ahead so the line from the ear opening to the lower edge of the eye socket is level.
4. Have someone place a flat object, such as a hardcover book, level on the crown of your head and mark the wall beneath it.
5. Measure from the floor to the mark with a rigid tape, then enter the result in whichever unit your tape uses.

Measure two or three times and use the average. A tape that sags or a book that tilts can easily add a centimeter of error, more than any conversion ever will.

What the numbers mean once converted

A converted height is more useful with context. The CDC's NHANES survey for August 2021 to August 2023 measured US adults aged 20 and over at an average of 175.1 cm (about 5′9″) for men and 161.2 cm (about 5′3½″) for women. Converting your own height and comparing it with those figures is a quick way to see whether you are above or below the national average, and the height percentile calculator turns the same comparison into an exact rank.

If you want to compare two heights rather than convert one, the height difference calculator gives the gap in centimeters, inches and percent. To see a converted height standing next to celebrities, fictional characters or friends, enter it in the 3D height comparison tool. For national averages in both units, see average height by country.

When to use a chart instead

The live converter is quickest for a single value. The full charts are better when you need to scan a range, for example to see every metric height that rounds to 5′7″, or to choose a size band. The cm to feet chart covers every centimeter from 120 to 230 cm, and the feet to cm chart covers every inch from 4′0″ to 7′6″. Both use exactly the same formulas as the converter, so the numbers always match.