Feet Versus Inches: How to Read Height Measurements

When comparing feet versus inches, how big is 12 inches? If you don't already know, then here's a hint: it's one foot. And how many feet are in a yard? It's three. But what if you have some other measure of length?

The larger unit describes the same length as the smaller. You'll need to understand their size relationship, or conversion rate, to establish how feet convert to inches.

Reading Feet and Inches Symbols

What you're looking at on your height chart is a combination of two units, with each labeled properly. These labels distinguish the proper characters for primes and double primes from their everyday keyboard substitutes. In formal typesetting, the correct characters are used because they’re distinct characters — just like you wouldn’t mix the letter "I" and the Roman numeral "i."

Let’s take an example. Five feet six inches is written as “5′ 6″.” There are two parts: five feet (5 ft) and six inches (6 in). The notation uses the prime symbol (′), also called the symbol of feet, and the double prime symbol (″), also known as the symbol of inches. You can find the corresponding abbreviations, feet (ft) and inches (in), above those symbols. That’s how we tell them apart.

You may see the apostrophe (') instead of the prime symbol, which is common in informal writing, or the double quotation mark (") instead of the double prime. Still, substitute marks and primes remain different characters, and using those substitutes for primes changes the typography, but not the measurement or its conversion.

Decimal Feet Versus Feet and Inches

Another way to express your height is decimal feet, where the decimal expresses a fraction of a foot. For example, if your height were listed as 5.6 feet, that would be 5 feet plus 0.6 of a foot. Multiply that by 12, and you’ll get 67.2 inches.

But 5.6 feet doesn’t equal 5 ft 6 in. Let’s work through the arithmetic.

Take the first example, 5.6 feet:

Multiply that number by 12, as there are 12 inches in a foot.

That gives us 67.2 inches.

Now consider the mixed notation of 5 ft 6 in:

Multiply the number of feet by 12 inches per foot, giving us 60 inches

Add the inches together: 60 + 6 = 66 inches

Arithmetic examples show why the two readings produce such drastically different lengths.

Converting Total Inches to Feet and Inches

So how do you recover the whole number of feet and remaining inches? Divide the positive total-inch value by 12, and the quotient is the number of feet. Then, the remainder will be the remaining number of inches.

This concept ties into how the site’s documented converter modes require certain inputs. In this case, I’m considering how the Feet & inches mode works: you enter the whole feet, then the remaining inches. That means the input is separate values. Alternatively, the Total inches mode requires you to combine the numbers. So instead of entering 5 and 6, you’d enter 66.

Sources

• Feet to Inches (ft to in) conversion calculator
• Prime (symbol) - Wikipedia