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Converting height between feet, inches and centimetres

Height is the conversion people get wrong most often, and almost always for the same reason: feet and inches look like a decimal number but are not one. Writing 5.10 for five feet ten inches produces an answer nine centimetres out. This guide sets out the correct method, the notation to use and the heights that come up most.

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Why feet and inches trip people up

Feet and inches form a mixed-radix system. There are twelve inches in a foot, so the inches part runs from 0 to 11 and then rolls over. Decimal notation assumes ten, which is where the confusion starts.

Written properly, five feet ten inches is 5′10″ — a prime for feet and a double prime for inches. If you type 5.10 into a converter expecting decimal feet, you get 5 feet 1.2 inches, or 155.45 cm, instead of the 177.8 cm you meant. That is a difference big enough to change a clothing size or a medical chart.

The conversion itself is straightforward once the parts are separate. Multiply the feet by 30.48, multiply the inches by 2.54, then add the two. Going the other way, divide the centimetres by 2.54 for total inches, take the whole number of twelves as feet and keep the remainder as inches.

Key facts

Exact factors

One foot is exactly 30.48 cm and one inch exactly 2.54 cm — no rounding is involved.

Notation matters

5′10″ means five feet ten inches; 5.10 feet is a different, shorter height.

Metric is the default

Medical records, passports and sports federations outside the US use centimetres.

Rounding convention

Heights are normally given to the nearest centimetre, so 177.8 cm is usually written as 178 cm.

Shoes count

Official measurements are taken barefoot, which is why listed athlete heights vary between sources.

Daily variation

Adults are up to two centimetres shorter by the evening as spinal discs compress.

How to get it right

1

Separate the parts

Note the feet and the inches as two distinct numbers.

2

Convert each

Multiply feet by 30.48 and inches by 2.54.

3

Add them together

The sum is your height in centimetres — for 5′10″ that is 152.4 + 25.4 = 177.8 cm.

4

Reverse when needed

Divide centimetres by 2.54, then split the total inches into twelves for feet and a remainder for inches.

Questions people ask

Exactly 177.8 cm. The calculation is (5 × 30.48) + (10 × 2.54) = 152.4 + 25.4.

Keep reading

TV & monitor screen sizes

What a screen size in inches actually measures, how wide each popular size really is, and how to check a TV fits before it arrives.

Weight: kg, pounds and stone

Convert body weight between kilograms, pounds and stone accurately — including why the 2.2 shortcut fails at higher weights.

Airline luggage limits

Cabin and checked baggage limits in both centimetres and inches, how airlines measure them, and where travellers get caught out.

Convert a specific height

Every common height from 4′10″ to 6′6″ has a page with the exact centimetre figure.

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