Height Calculator

Two jobs in one height calculator

This page does two things that people ask for with the same three words. It converts a height between feet and inches, centimeters and meters, and it predicts how tall a child will grow from the heights of both parents.

Both answers come from short, standard formulas, and both are shown in every common unit at once, so you never have to convert twice. Type 5 feet 9 inches and you get 69 inches, 175.26 centimeters and 1.7526 meters. Type the parents' heights and you get a target for a son and a target for a daughter, plus the range that surrounds each one.

If you only need a unit swap, the inches to centimeters converter does it in one step. If you are measuring something that grows in a yard rather than in a house, the tree height page uses shadows and a sighting angle instead of a tape measure. This page is about people.

The conversion is exact: 2.54 centimeters per inch

There is no rounding in the unit conversion. Since 1959 the international inch has been defined as exactly 2.54 centimeters, and the foot as exactly 0.3048 meters, which is the number the National Institute of Standards and Technology publishes for the international foot.

So a height in feet and inches becomes centimeters in two moves. First turn feet into inches: 5 feet 9 inches is 5 x 12 + 9 = 69 inches. Then multiply by 2.54: 69 x 2.54 = 175.26 centimeters, which is 1.7526 meters.

Going the other way is one division. Someone who is 180 centimeters tall is 180 / 2.54 = 70.87 inches. Take off the five whole feet, 60 inches, and 10.87 inches remain, so the height is 5 feet 10.87 inches.

The common error is dividing when you should multiply. Centimeters are smaller than inches, so a centimeter height is always the larger number: 69 inches is 175.26 centimeters, never 27 centimeters. If the answer got smaller, the operation was upside down.

A conversion table for the heights people look up

These are the heights that show up in forms, sports rosters and doctor visits. Centimeters are rounded to one decimal and meters to two, so the last digit can differ from a calculator that keeps more places.

Every step of two inches adds 5.08 centimeters, which is why the centimeter column climbs in even steps of about five. Every step of four inches adds exactly 10.16 centimeters, the figure used in the chart above.

Metric countries write the same heights differently: 1.83 meters instead of 183 centimeters, and 1.83 m instead of 6 feet. A passport or a driver license form that asks for meters wants the decimal point two places to the left of the centimeter figure.

Predicting a child's adult height: the mid-parental formula

The standard method is the mid-parental height, and the American Academy of Pediatrics explains it on HealthyChildren.org. Add the two parents' heights in inches, divide by two, then adjust by five inches in the direction of the child's sex.

For a son: (mother + father + 5) / 2. For a daughter: (mother + father - 5) / 2.

Take a mother who is 5 feet 4 inches (64 inches) and a father who is 5 feet 10 inches (70 inches). For a son: (64 + 70 + 5) / 2 = 69.5 inches, which is 5 feet 9.5 inches. For a daughter: (64 + 70 - 5) / 2 = 64.5 inches, which is 5 feet 4.5 inches.

The five inches is the average adult height gap between men and women, split evenly around the parents' midpoint. In centimeters the same formula adds or subtracts 13, because 5 inches is 12.7 centimeters and the published metric version rounds to 13.

Notice that the two targets in each row sit five inches apart, and the pair is centred on the parents' average. That is the whole method: a midpoint plus a sex adjustment, nothing more.

What the prediction can and cannot tell you

The American Academy of Pediatrics calls the mid-parental method a rough estimate and puts the margin of error at about four inches up or down. For the example above, that means a son's likely adult height runs from 65.5 to 73.5 inches, or 5 feet 5.5 inches to 6 feet 1.5 inches. In centimeters that is 166.4 to 186.7.

A range that wide is the honest answer. Height comes from many genes, not one, and the same parents can produce children who land at opposite ends of it. Nutrition, sleep, chronic illness and the timing of puberty move the result too, which is why two siblings with the same target often differ by two or three inches.

The formula says nothing about growth disorders. A child who is tracking well below the family target, or whose growth curve crosses percentile lines, needs a pediatric visit rather than a better calculator. The same is true of a child who stops growing or starts puberty unusually early or late.

Use the number as a conversation starter with a pediatrician, and use the range, not the midpoint, when you talk about it. Nobody's adult height is decided by a two line formula.

How tall are US adults?

The Centers for Disease Control and Prevention publishes measured heights from the National Health and Nutrition Examination Survey. Its FastStats body measurements page, using data collected from August 2021 to August 2023, puts the average American man at 68.9 inches (175.0 centimeters) and the average American woman at 63.5 inches (161.3 centimeters).

Those are measured heights, taken with a stadiometer, not self-reported ones. Self-reported heights run a little high in surveys, mostly among men, which is one reason you see rounder figures quoted elsewhere.

An average is a midpoint, not a target. Half the adult population sits above it and half below, and a 5 foot 6 inch man is a normal man, not a short one in any medical sense. The number is useful for context and for clothes sizing, and it is not a standard anyone has to meet.

Measuring height so the number means something

A height is only comparable if it was taken the same way twice. Stand without shoes, heels together and flat, back against a wall, looking straight ahead with the chin level. A book or a flat board on top of the head, marked against the wall, works better than balancing a tape measure on your own head.

Children under two are measured lying down, because standing is not reliable at that age. That is why a pediatric visit switches from length to standing height at the second birthday, and why a chart can look like it dropped a centimeter that day. The switch is a change of method, not a change in the child.

Adults measure slightly shorter in the evening than in the morning, because the discs between the vertebrae compress during the day and recover overnight. One measurement is enough for a form; for tracking, pick a time and stick with it.

Unit mistakes are the other quiet source of error. A metric tape marked in centimeters read as inches turns 5 feet 9 inches into 27 inches of nonsense, and a height typed as 1.75 instead of 175 in a centimeter field becomes a toddler. The widget accepts either system, but only one of them at a time.

Height, weight and BMI

Height is the input most people forget in weight math. Body mass index is weight in pounds times 703, divided by height in inches squared. At 180 pounds and 70 inches: 703 x 180 / 4,900 = 25.8.

Change only the height and the index moves a lot. The same 180 pounds at 68 inches is 703 x 180 / 4,624 = 27.4, which crosses from overweight into a different band on most charts. A tall person carries more weight at the same index, and a short person carries less, which is the known weakness of BMI at the extremes.

That is why this page reports inches to two decimals. Rounding 68.9 down to 68 changes the squared term by about 3 percent, and in a BMI calculation that is enough to shift the answer. Convert first, then run the BMI calculator with the exact figure.

None of this is a diagnosis. BMI is a screening number, and a doctor reads it next to waist measurement, muscle mass and history. For a child, the pediatric growth chart matters more than any adult index.