How to measure your height accurately at home, in cm and feet-inches

What you need

• A hard, flat wall with no skirting board in the way, or a door frame.
• A hardcover book or a flat ruler to mark the top of the head.
• A pencil or removable tape, and a metal or fiberglass tape measure with both centimeters and inches.
• A helper. Measuring yourself is possible but less reliable, because you cannot see the mark while standing still.

Steps for a good measurement

• Take off shoes, hats and hair accessories, and let hair lie flat.
• Stand with your back to the wall, feet together, heels, buttocks, shoulders and the back of the head touching the wall if they can.
• Look straight ahead with the chin level, not tilted up or down. A tilted head changes the reading.
• Have the helper lay the book flat on top of your head, pressed gently against the wall, and mark the wall under its lower edge.
• Step away and measure from the floor to the mark with the tape held vertical, starting the tape at zero on the floor.
• Repeat twice more and use the middle value, or the average, to remove small mistakes.

Reading the tape in cm and in inches

Metric tapes are marked in millimeters, so you can read the result directly to 0.1 cm. Inch tapes are usually marked in eighths or sixteenths. To use an inch reading, convert it to a decimal first and multiply by 2.54. Eighths of an inch in centimeters are:

A worked example

Say the tape shows 5 ft 7 1/4 in. That is 5 × 12 + 7 + 1/4 = 67.25 inches. Multiply by 2.54 and you get 170.82 cm, so 170.8 cm to the nearest tenth, or 171 cm when a form asks for whole centimeters. For the conversion of any reading, use the feet and inches to cm converter.

Going the other way, if a doctor's form says 172.5 cm, divide by 2.54 to get 67.91 inches, which is 5 ft 7.9 in. The cm to feet and inches converter does this directly, and the cm to feet and inches cheat sheet lists whole centimeters.

Common mistakes

• Measuring against a wall with a skirting board, which keeps the heels away from the wall and adds a few millimeters.
• Letting the book tilt, so one edge sits higher than the other. Check it is level against the wall mark.
• Reading the tape from the wrong end. Many tapes have a metal tab that moves slightly, and it is meant to; start from the floor, not from the tab edge.
• Mixing units mid-reading, for example reading 67 inches and adding a centimeter value. Convert once, at the end.
• Rounding too early. Keep all decimals until the last step: 5 ft 7 1/4 in is 170.82 cm, but if you first round to 67 inches you get 170.18 cm, a loss of 0.63 cm.

How much does rounding matter?

Rounding a height to the nearest whole centimeter moves it by at most 0.5 cm, which is 0.2 inch. Rounding to the nearest whole inch moves it by at most 1.27 cm. For most forms either is fine, but when a form asks for centimeters, report the centimeter figure you measured or converted rather than a number derived from rounded feet and inches. The reference definition behind all the numbers is 1 inch = 2.54 cm exactly, from NIST SP 811 and the BIPM.

Children, and measuring more than once

Children move, so take three readings and use the middle one, and record the date next to each so growth can be compared over time. When tracking height in both units, store the centimeter figure and convert for display, since that avoids repeated rounding. A side-by-side reference is in the height chart from feet and inches to cm, and the inches to cm chart covers smaller fractions.

Where this fits in the series

This is the third post in the height series. It follows the feet and inches height chart and the cm to feet and inches cheat sheet. If you measure other things with a tape, such as wrench or drill sizes, see socket and wrench sizes.