What is the Size of a Ruler? Complete Guide

Rulers are a ubiquitous tool that we use in our daily lives for measuring length and distance. But have you ever stopped to wonder about the size of a ruler? The size of a ruler can vary depending on its intended use and the measurement system it employs.

The standard length for most rulers is 12 inches (or 30 centimeters), excluding the slight margins on either end of the ruler. However, yardsticks measure three feet (36 inches), and meter sticks measure one meter (100 cm). These measuring tools are used for different distances.

In this article, I will explore the various sizes of rulers available and their common uses, as well as the different measurement units they may employ. 

How Big Is a Ruler?

A ruler can come in different sizes, but a typical one that you might use in school or at home to measure things is usually around 12 inches or 30 centimeters long. 

It’s usually about an inch or 2.5 centimeters wide and may have markings in both inches and centimeters or in one or the other. However, there are also smaller rulers that are a few inches long, and larger ones that can be several feet long for measuring larger objects. 

Rulers can also come in different shapes, such as triangular or flexible ones, for different purposes.

Different types of Rulers and their Sizes


Standard Ruler Sizes

The most common type of ruler is the standard ruler, which is typically 12 inches long and 1 inch wide. Standard rulers are used to measure both length and distance in the United States. However, other countries may use different standards. For example, a standard ruler is 30 centimeters long in the UK.

Metric Ruler Sizes

Metric rulers are used in countries that follow the metric system of measurement. Metric rulers are typically 30 centimeters long and have markings for millimeters and centimeters. Some metric rulers may also include markings for inches.

Small Ruler Sizes

Small rulers are typically used for precision measurings, such as in the fields of engineering and science. Small rulers can range from 6 inches to 12 inches in length and can be made of various materials, including metal, plastic, and wood.

Large Ruler Sizes

Large rulers are used for measuring longer distances, such as in the construction industry. Large rulers can range from 24 inches to 48 inches long and are typically made of wood or metal.

Foldable Rulers

Foldable rulers are convenient to use and store as they can be easily folded to a smaller size. They are typically 6 inches or 12 inches long and can be made of various materials, including plastic and metal.

Flexible Rulers

Flexible rulers are made of plastic or rubber and can be bent to follow curved surfaces. They are typically used in the fashion industry for measuring body contours.

Wooden Rulers

Wooden rulers are durable and can be easily customized with engravings or paintings. They are commonly used in schools and offices and are available in various sizes, including 6 inches, 12 inches, and 18 inches.

Plastic Rulers

Plastic rulers are lightweight and affordable. They are commonly used in schools and offices and are available in various sizes, including 6 inches, 12 inches, and 18 inches.

Metal Rulers

Metal rulers are durable and have a longer lifespan than plastic or wooden rulers. They are typically used in the construction industry and are available in various sizes, including 12 inches, 24 inches, and 48 inches.

Digital Rulers

Digital rulers have electronic displays that show the measurement in either inches or centimeters. They are commonly used in the field of engineering, and some models may include additional features such as a level or angle measurement.

Engineer Rulers

Engineer rulers are typically 12 inches long and have markings for various scales, including 1:10, 1:20, and 1:50. They are commonly used in engineering and architecture for drafting and design.

Architect Rulers

Architect rulers are typically 18 inches long and have markings for various scales, including 1/16 inch, 1/8 inch, and 1/4 inch. They are commonly used in the field of architecture for drawing plans and blueprints.

Measuring Tape

Measuring tapes are a type of ruler that is flexible and can be rolled up for easy storage. They are typically used in construction and home improvement projects, and they can range from 12 feet to 100 feet in length.

Do Rulers Differ From Other Measuring Tools?

Rulers are one type of measuring tool that is used to measure the length or distance of an object. While there are many other types of measuring tools available, here are some key ways that rulers differ from other measuring tools:


Calipers are more precise than rulers and are used to measure the distance between two points on an object. They can also be used to measure the diameter of an object.


Protractors are measuring tools that are used to measure angles. They have a half-circle shape with a rotating arm that can be used to measure the angle between two lines.

Measuring Cups and Spoons: 

These are measuring tools used to measure liquid or dry ingredients in recipes. They are typically marked with volume or weight measurements and are used in cooking and baking.

Laser distance meters: 

These high-tech tools use lasers to measure distances quickly and accurately. They are commonly used in construction and other industries where precise measurements are needed.

How to Read a Ruler?


Reading a ruler is essential for anyone who needs to measure objects in both inches and centimeters. When measuring an object using a ruler, it’s important to pay attention to the small lines between the whole numbers. 

These lines show fractions or decimals and can greatly affect the accuracy of the measurement. 

So, it’s essential to learn how to read the ruler and the lies on it to get the exact measurement of the object.

Fractions of an Inch:

Ruler markings are very precise and often measure objects with accuracy, usually in 1/8th or 1/16th inch increments. Between two-inch points, there are either seven or fifteen marks, which represent 1/8th or 1/16th of an inch, respectively.

If you look closely at the ruler markings, you’ll see a line in the middle that shows the half-inch mark. The quarter-inch marks are shorter and are between the half-inch mark and the nearest inch. These marks help you measure more accurately than just using whole inches. The 1/8th-inch marks are even smaller than the quarter-inch marks, and there are even tinier 1/16th-inch marks between them.

The more markings a ruler has, the more precise its measurements will be. But having more markings can also cause confusion, especially when trying to read tiny marks like 1/8th and 1/16th-inch marks.

One way to simplify the process is by examining the length of the markings. Typically, half-inch marks will be longer than quarter-inch marks, which will be longer than 1/8th-inch marks, and 1/16th-inch marks will be the shortest of them all.

Fractions of a Centimeter

The metric system uses 10 millimeters per centimeter, making it easy to measure accurately. On the metric side of a ruler, there are nine marks between each centimeter, with each dot representing 1/10th of a centimeter. This helps you easily determine the exact measurement of an object.

If you take a closer look at a metric ruler, you’ll notice that there is a half-centimeter line between two-centimeter marks. This line is located down the center of the centimeter marks and is slightly longer than each millimeter line.

How to Measure Objects Using A Ruler?

Measuring objects using a ruler is a simple process that can be done by following these steps:

Choose the right ruler: Select a ruler that is appropriate for the object you want to measure. For small objects, use a standard or metric ruler. For larger objects, use a long ruler or measuring tape.

Align the ruler: Place the ruler next to the object you want to measure. Align the starting end of the ruler with the edge of the object.

Read the markings: Look at the markings on the ruler that align with the edge of the object. If using a standard ruler, read the markings in inches or fractions of an inch. If using a metric ruler, read the markings in millimeters or centimeters.

Record the measurement: Write down the measurement in a notebook or on a piece of paper.

Repeat for accuracy: If you need to be precise, measure the object several times and take an average of the measurements.

By following these steps, you can accurately measure objects using a ruler.

Which Is Better, A Footlong Ruler Or A Yardstick?

A yardstick is a specialized type of ruler that is designed to measure objects up to a yard in length or 36 inches. While it shares the same 1/8th or 1/16th markings as a standard 12-inch ruler, the yardstick’s distinguishing feature is its impressive length.

Carrying a yardstick around with you can be inconvenient, as it is three times as long as a standard ruler and not easily transportable, particularly if you are traveling with a backpack. Typically, you will only need to use a yardstick when measuring items that are longer than 3 feet, as shorter measurements can be achieved with a standard ruler.


What is the size of a standard ruler?

The size of a standard ruler is typically 12 inches or 30 centimeters long, and about 1 inch or 2.5 centimeters wide.

Is a ruler 12 cm?

No, a standard ruler is usually 12 inches or 30 centimeters long. However, there are rulers that are specifically designed to measure in centimeters, and these rulers maybe 12 cm long.

Are rulers in cm or mm?

Rulers can be found in both centimeters and millimeters, depending on the intended use. Standard rulers in the United States usually measure in inches, while rulers in countries that use the metric system of measurement usually measure in centimeters and millimeters.

Why is a ruler 12 inches?

The standard ruler is 12 inches long because it was based on the traditional English measurement system. This system was used in the United States until the 1970s when the metric system was officially adopted.

What is 1 ruler equal to?

One ruler is equal to 12 inches or 30 centimeters, depending on the measurement system being used. Rulers may also have additional markings for measuring smaller increments, such as millimeters or fractions of an inch.

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