Understanding the Feet and Inches Symbol + Conversions

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Most people write measurements using the metric system, so it’s not a surprise many woodworking references are based on it. The only problem is it makes newbies confused when converting dimensions from feet and inches symbols. 

Here’s a brief discussion to help you save time and prevent making the wrong measurements for your next project. 

What’s the Feet Symbol?

The symbol for feet often comes up when you need to buy lumber, shingles, or pipe. You can write feet in two ways: either in its abbreviated form “ft” or its marking in the form of a single apostrophe (‘).

symbol for feet

Typically, the measurement dimensions in a lumber yard are often written symbols for feet and inches. For example, a wooden board with the exact size of 2 in. x 6 in. x 12 ft. reads as a material that’s 2 inches thick, 6 inches wide, and 12 feet long. 

Remember that the symbols “ft” and single apostrophe (‘) denote feet not only in their plural form but also in their singular variation. This condition means that one foot and five feet can use the “ft” abbreviation. 

Are Lumber Board Length Measurements in Feet Precise?

If you’ve been a woodworker long enough, you’d know wood materials don’t often align with their listed dimensions. These issues often come up when dealing with the lumber’s width and length. 

For example, a board with listed dimensions of two inches thick and six inches wide doesn’t have these exact specifications if you get it measured. At best, this wood material’s actual size is 1 ½ inches by 5 ½ inches because it has gone through manufacturing. 

The good news is these procedures often don’t affect the lengths of the boards you’ll get from your nearest lumber yard. If you bought a piece of wood that’s eight feet in length, the measurements on its label wouldn’t be different from its actual size. 

cutting lumber with table saw

Even if the material is labeled 8 inches tall instead of symbols for feet, it doesn’t indicate that the board has an inaccurate length measurement.   

Centimeters Per Foot

Since most people use the metric system, you’ll encounter many materials labeled in centimeters (cm) and meters (m). It may sound intimidating, but the metric system is easy to understand because it’s measured in ten units. 

The confusion often comes from converting centimeters to feet, a unit from the imperial system. 

To convert feet, my best advice is to break them into inches. By this, you should take note of the equivalency of twelve inches to one foot. 

With one inch equivalent to 2.54 centimeters, the next step you ought to do is convert feet into inch measurements. Try to multiply 2.54 by 12, and you’ll get the answer of 30.48 centimeters. If you round that off, it shows that a single foot equals 30 centimeters. 

tape measure and pen

Meanwhile, one meter has an equivalency of around three feet. You’ll notice that one yard and meter include similar measurements. 

How to Convert Feet to Centimeters

Now that you know how to convert ft to cm, it’s time to learn how to do it the other way around. For this method, you must write inches instead of feet. 

For example, you want to convert five feet into centimeters. You can do this conversion by multiplying the feet measurements by 12, which leads to 5 times 12 equals sixty inches. 

After that, you must multiply sixty inches by 2.54 to get the equivalent centimeters. From there, the answer will be 243.8 cm. 

What’s the Inches Symbol?

It’s easy to confuse feet and inches because they have similar symbols. As you know, the symbol for feet is written in a single apostrophe (‘). Meanwhile, the symbol for inches goes in the form of a double apostrophe (“). 

symbol for inches

Take height measurements like 5’ 10” as an example, where the number with single quotation marks after is read as 5 feet. The number followed by the double apostrophe, here 10”, represents ten inches. So, the height in this example is 5 feet 10 inches.

So if you start second-guessing what the symbol for inches is, don’t forget that it’s the one with double quotation marks.  

How Inches is Abbreviated

Now that we discussed the foot and inch symbols, it’s time to tackle the abbreviations[1] for this unit of measurement. 

Instead of an inch symbol, you can write one inch with “in” as its shortened term. Sometimes, you’ll encounter people adding an extra (“ins”) at the end of the word. Here’s an example to help you understand how the inches abbreviation works: 

man writing down on notebook in a workshop

If you went to a wood shop and saw boards marked 4 ft. and 5 in., you should know that it reads as four feet and five inches long. 

Centimeters Per Inch

Since this unit doesn’t belong to the metric or international system, converting inches can be challenging for some people. When the measurement of one material does not match the other, it can compare to communicating with different languages. 

For example, you’re working on installing a sink with measurements written in centimeters or meters. The problem will arise if the kitchen top has specifications in inches. 

Fortunately, you can convert inches to centimeters easily. All you need to do is remember that an inch is equivalent to 2.54 centimeters. 

tape measure and pencil

Let’s formulate an example below to help you convert inches better: 

First, let’s say you have a pipe that’s 15 inches thick and want to convert this specification into cm. Unlike converting feet, this method only requires you to multiply that 15 inches by 2.54. It will lead you to the answer that 15 inches have the same value as 38.1 centimeters.

Prime Mark History

While it’s true that prime marks are used in mathematics, it’s also a term used in feet and inches to describe the written order of height and length. 

Feet measurements are typically considered the prime symbol because they’re always mentioned first. Because of this, they come with a single prime mark. 

And since inches come in the second order, they’re represented with double prime symbols. Don’t forget that smaller prime marks often take up less space, making them easier to use and read. 

measuring wood

Single prime and double prime marks are common, but you’ll encounter triple prime marks in ligne indications. 

How It’s Written

Many people confuse prime marks with quotation marks or apostrophes. However, double or single prime marks are written on a straight left edge, slightly slanted to the right. 

Since modern keyboard doesn’t have dedicated options for prime symbols, it’s only natural that these marks are typed or written in quotations and apostrophes. 

Use of Prime Mark

Besides measurements, prime marks also represent angles. In arcminutes, a single prime mark denotes 1/60 of a degree. Meanwhile, double-prime refers to arcseconds or 1/60 of an arcminute. 

tape measure and pen

You can also use prime marks as symbols for time. Double prime often indicates seconds, whereas single prime is the minute symbol. 

Why Do We Use Inches and Feet for Units of Measurement?

Unlike other measurements shortened from a word,  you can write feet and inches in symbol forms. The reality that the symbol for feet is an apostrophe and inches come with quotation marks makes these units easy alternatives that save time and space. 

Why Should You Understand the Symbols?

Examples

Not everyone is an industry expert, but most manufacturers, in-store or online, don’t bother putting the whole spelling of measurements in their products. Generally, you’ll encounter specifications with written symbols. 

And given that feet and inches have similar symbols, it’s only natural that you get confused between them. Here’s another example to shed light on this:  

measuring with Swanson Tool Co TC130 6-Inch Combo Square

You’re instructed to buy material with 2 x 8 x 16’ specifications. What does this mean? The measurement refers to a workpiece with sizes around 2 inches thick, 8 inches wide, and sixteen feet long. 

Once you understand this method, you won’t have difficulties differentiating feet and inches from one another. 

Symbols vs. Abbreviation

Symbols offer a clear advantage in certain situations, and here’s why they’re often preferred over abbreviations:

Speed

In woodworking, every second counts. From personal experience, this craft requires meticulous attention and can be time-consuming. Using symbols for marking measurements is quicker than writing out abbreviations. This minor adjustment can save crucial moments, allowing you to resume your work with minimal delay.

Space-Saving

If we talk in the simple logic of writing, a mark consumes less space than an abbreviation. This logic also applies when working on a blueprint for your project because it would prompt you to include material specifications. 

man writing down on notebook in a workshop

While there’s no harm in writing feet and inches in their complete spelling, these words can crowd the blueprint and lead to confusion. 

Comprehension

No matter what language you’re using, symbols don’t change their uses or meanings. Meanwhile, it’s crucial to note that abbreviations can have different definitions in other languages. 

How are Lumber Board Dimensions Measured?

Quarters Sizing

Most rough-sawn materials are sold in quarters. If you don’t know what that means, it simply refers to the thickness of the lumber measured in quarter increments. You’ll see wood pieces labeled in “4/4,” which means they’re cut in 4 quarters or an inch thick. 

Dimensional Sizing

These measuring methods are often used in DIY crafting and construction. You’ll also encounter these dimensions in wood shops, selling lumber and other wooden materials in inches. 

Board Foot Sizing

You should understand how Board-Feet sizing works if you’re buying rough-sawn lumber in bulk. It’s sold in 144 cubic feet measurements, so expect it to be cheaper. 

measuring log before cutting

Should I Purchase Lumber With Exact Measurements?

It’s nearly impossible to buy wooden boards with accurate measurements, especially in standard sizes like 2×4 or 2×6. If you’re seeking materials with exact dimensions, I’d recommend you to opt for specialty wood boards.

You can typically find these specialty boards at local hardware stores. However, keep in mind that they might come with a heftier price tag. But in return, you’re investing in accuracy and precision.

Is the Width of Lumber in Inches Accurate?

No matter what unit the materials are measured in, the reality is not every size on their labels is accurate. While length specs are often precise, I can’t say the same for thickness and width after it has gone through the manufacturing process. 

Also Read

FAQ

How should you write height in the form of feet and inches?

You can write height in feet by its abbreviation (ft) or its prime mark (‘). Meanwhile, height in inches is written in its (in) or (ins) abbreviation. You can also refer to it in its double prime sign (“).

How does the imperial system differ from the metric system?

The metric system comprises divisible figures from numeric progressions of millimeters, centimeters, and meters. One significant advantage of the metric system is its decimal-based structure, making conversions between units more straightforward.

On the other hand, the imperial method follows a pattern of inches, feet, and yards. It often involves complex conversions with varying conversion factors.  

How many inches are in one foot?

There are 12 inches in every foot, which you can say is a bit longer than a roman foot. You may not know, but it’s an old quantification of 11.64 inches. 

Conclusion

A common pitfall for woodworking beginners is misinterpreting the feet and inches symbols. Once you grasp the distinction between these two, I’m confident it will greatly enhance your precision in your craft.

This know-how can also save you money and time in the long run since you’ll buy the right measurement material. 

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Robert Johnson is a passionate furniture maker & carpenter, sought after for his knowledge on the craft.
You’ve probably seen his down-to-earth wisdom in USA Today, Bobvila, Family Handyman, and The Spruce, where he has shared commentary and guidance on various woodworking topics.

Robert is the brain behind Sawinery, where he aims to share tips, tricks, and a passion for all things carpentry.

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