Cm to Inches — Convert Metric Health Measurements

One centimeter is 0.393701 inches. The relationship is exact in the other direction — NIST defines the inch as precisely 2.54 cm — so dividing centimeters by 2.54 gives an answer limited only by how far you round it. A height of 170 cm comes out at 66.93 in.

The threshold trap: 102 cm is not 40 inches

Centimeters usually reach an American reader attached to a health number — a waist cutoff in a research paper, a measurement from a clinic abroad, a chart in an international guideline. The temptation is to convert your figure and compare it against the American threshold. That can flip the answer.

Waist circumference is the clearest case. The NHLBI states that risk rises above 40 inches for men and 35 inches for women. Internationally the same idea is published as 102 cm and 88 cm. Convert and they do not line up:

Threshold in inches	Exact equivalent	Metric threshold in use
40 in (men)	101.60 cm	102 cm
35 in (women)	88.90 cm	88 cm

Neither pair was derived from the other. Each system rounded to a number people can remember, and the rounding went in opposite directions for men and women. A woman measuring 88.5 cm is under the American cutoff of 35 in and over the metric one of 88 cm — the same tape, two verdicts. At the edge, say which threshold you are using rather than converting your way to a different one.

Centimeters to inches at a glance

Centimeters	Inches
1 cm	0.39 in
10 cm	3.94 in
40 cm	15.75 in
88 cm	34.65 in
100 cm	39.37 in
102 cm	40.16 in
160 cm	62.99 in
170 cm	66.93 in
180 cm	70.87 in

Height needs a second step

A person’s height in centimeters converts to a single number of inches, which is not how anyone in the US says it. To get from 170 cm to “5 ft 7 in,” divide the 66.93 inches by 12: five whole feet, with 6.93 inches left. Rounding that to 7 makes the height 170.2 cm — an eighth of an inch of drift, invisible for conversation and enough to move a BMI by a hundredth.

Going in the reverse direction, feet and inches to meters does both steps at once, since metric height is what BMI and body-surface-area formulas actually take.

Round once, at the end

The most common error on this page is not the factor. It is rounding twice: turning 170.4 cm into 170, then 170 into 66.9, then 66.9 into 67. Each step is defensible and together they move the result by nearly a centimeter.

Convert from the number you measured, and round only when you write the answer down. If you measured to the nearest half centimeter, report inches to one decimal place and stop there.

For the opposite direction and the metric forms that ask for it, see inches to cm. For the weight half of the same conversion, pounds to kg.

This content is informational. Waist and other clinical measurements should be interpreted by a health professional, in the units their guideline uses.