What is Ruler?
Are you someone who looks at a ruler but doesn't understand how to use it? or do you ever wonder why so many different types of rulers are used? Why can’t just one ruler of 15 cm be sufficient? Vedantu will answer all these questions below. In this article, you will learn what is a ruler, its type, reading a ruler, and its uses.
Ruler Meaning in Maths - A ruler is a device or tool that is used in geometry and technical drawing, as well as engineering and construction technologies to measure the distance of a straight line. A math ruler is used to measure the length in both metric and customary units. The rulers are marked with standard distance in centimetres in the top and inches in the bottom and the intervals in the ruler are called hash marks.
Types of Ruler
There are different types of ruler depending on the material it is made of. Rulers are made from wooden, plastics and metal. Plastics are used to make rulers since they were invented as they could be moulded with length markings. Material rulers are used at a mechanical workshop. Sometimes a metal edge is embedded into a wooden desk ruler to preserve the edge when used for straight-line cutting.
Depending on the size of the ruler there are two types of ruler - a short ruler and a long ruler. Short rulers are 15 centimetres which are very convenient to carry and long rulers are 30 centimetres or 12 inches long, it is useful to draw larger drawings.
Line Gauge - This ruler is used in the paint industry and is made from a variety of materials, typically metal or clear plastics. The basic unit of measurement in the basic line gauge includes inches, agate, picas, and points.
Measuring Instruments - This instrument is made similar to the ruler function and they are portable by folding or retracting into a coil as in metal tape measure. When they are extended to use, It is straight as a ruler. For example, you can take a carpenter's ruler which is 2 m long and when it is folded, it's just 25 cm long, so that it can easily fit into the pocket.
Flexible Length Measuring Length - This instrument does not need to be straight, it is used by tailors to measure the fabric. The length of the tape is calibrated by inches and centimetres. It is used by a tailor to measure the solid body length, for example, a person's body. As well as linear length measurement, for example, a person's leg.
A Contraction Ruler - In this ruler there are larger divisions compared to the standard division, to allow the shrinkage of the metal casting. The contraction ruler is also known as the shrinkage or shrink ruler.
Screen Rulers - It is a type of ruler software programme, where you can have a digital scale on the screen by setting up the pixel. They are functional in both mobiles and the computer and it is useful in the absence of a physical ruler.
Measuring Objects Length using Ruler
To measure the length of any object, primarily place the first hash mark (which is at Zero marking) of the ruler, exactly at one end of the object. Then set the object along the ruler and then finally note down the final hash marks, which is the endpoint of the object. Refer to the above diagram for a better understanding of the process.
Reading Ruler
Ruler Measurements in Centimetre - A ruler will be having centimetre and millimetre markings. A centimetre is smaller compared to an inch. The hash marks with numbers on the upper side represent the centimetre. The millimetre is smaller than the centimetre, the smaller hash in between centimetres is known as a millimetre.
10 millimetres is equal to 1 centimetre.
1/10 = One-tenth of the cm.
3/10 = Three tenth of cm.
5/10 = Five tenth of cm.
8/10 = Eight tenth of cm.
1 is equal to 1cm.
Ruler Measurements in Inches - Inch is bigger than the centimetre. The big long hash with numbers opposite to the centimetre is known as the inches. There are a total of 16 sub hashes between the marking of one inch on the ruler.
Uses of a Ruler
After going through what is the ruler? We understood that ruler in maths is used to measure a line and the straight edges, which allows them to be used for drawing, scoring, and cutting. Many times they are also used in engineering, carpentry and the print fields.
Uses of Rulers in Geometry
In geometry, a ruler without having any marks on them could be used for drawing only a straight line between two points. It is also used to draw graphs and tables due to its straight edge.
It is used in the ruler and compass construction, where an unmarked ruler and compass can be used for construction. It is also useful in bisecting the angle by using an unmarked ruler and compass.
Do You know?
Which is the largest preserved ruler? Copper alloy rod is the oldest preserved ruler from c. 2650 BCE and it was by the German Assyriologist Eckhard Unger while excavating at Nippur.
Conclusion
A ruler is a tool that you will be encountering multiple times in your academic life. Each time it will come across in a different format and different least count, but the basic way of reading will remain the same.
After reading this article we have become aware of the importance of a ruler, its type and how it is read. Ruler is the most basic tool of geometry and also the most important one because only after learning to read it, you can proceed towards using other tools.
FAQs on Ruler
1. What is a ruler in Maths?
A ruler is a fundamental tool in geometry used for measuring distances and drawing straight lines. It is a straightedge marked with standard units of length. Most rulers used in school show both centimetres (cm) on one side and inches (in) on the other, allowing for precise measurement and the construction of geometric figures as per the CBSE/NCERT curriculum.
2. What are the main markings on a standard classroom ruler?
A standard classroom ruler typically shows two different measurement systems:
- The Metric System: This side is marked in centimetres (cm). Each centimetre is further divided into 10 smaller, equal units called millimetres (mm).
- The Imperial System: The other side is marked in inches (in). Each inch is usually divided into smaller fractions, such as 1/2, 1/4, 1/8, and 1/16 of an inch.
The '0' mark indicates the starting point for any measurement.
3. How do you correctly measure the length of an object with a ruler?
To measure an object accurately, follow these essential steps:
- Align the Ruler: Place the ruler parallel to the object you wish to measure.
- Start at Zero: Align the 'zero' mark (0) of the ruler with one end of the object. A common mistake is starting from the physical edge of the ruler, which may not be the zero point.
- Read the Measurement: Look at the other end of the object and read the corresponding measurement on the ruler's scale.
- Avoid Parallax Error: Ensure your eye is positioned directly above the marking on the ruler to get a correct reading. Viewing from an angle can make the measurement appear different.
4. What are some common mistakes to avoid when using a ruler?
To ensure accuracy, it's important to avoid these common mistakes:
- Starting from '1': Always begin your measurement from the zero mark (0), not the 1 cm or 1-inch mark.
- Using a Damaged Ruler Incorrectly: If the zero mark on your ruler is broken or faded, you can start from another whole number (like 2 cm). Measure the object and then subtract your starting number (2 cm) from the final reading.
- Reading at an Angle: Looking at the scale from the side can cause a parallax error, leading to an incorrect reading. Always view the measurement from directly above.
- Using a Tilted Ruler: The ruler must be perfectly parallel to the object's edge to measure its true length.
5. Beyond drawing lines in Maths, what are the practical applications of a ruler?
Rulers are essential tools with numerous real-world applications across various fields:
- In Science, they are used to measure plant growth, the length of specimens, and in physics experiments.
- In Art and Design, rulers are crucial for creating precise sketches, technical drawings, and architectural models.
- In Crafts and Tailoring, they are used for accurately measuring fabric and other materials.
- In Carpentry, larger rulers and tape measures are fundamental for cutting wood and building structures.
- At home, they are used for everyday tasks like checking furniture dimensions or hanging picture frames straight.
6. Why do most rulers have both inches and centimetres marked on them?
Rulers often feature both inches (Imperial system) and centimetres (Metric system) to be versatile. The Metric system (cm, mm) is the global standard for science and is used in the Indian education system as per the CBSE 2025-26 guidelines. However, the Imperial system (inches) is still common in some countries (like the USA) and for specific commercial products like electronic screen sizes (e.g., a 6-inch phone) and clothing. Having both scales on one ruler allows for easy conversion and wider applicability. For reference, 1 inch is approximately 2.54 centimetres.
7. How does the accuracy of a phone's ruler app compare to a physical ruler?
A physical ruler is significantly more reliable and accurate for most tasks, especially for schoolwork. Here's a comparison:
- Physical Ruler: Its markings are printed to a precise, fixed standard. It is the required tool for academic work, technical drawing, and crafts where accuracy is critical. The main potential for error comes from incorrect human use (e.g., parallax error).
- Ruler App on a Phone: Its accuracy depends on the screen's pixel density and software calibration, which can vary. While useful for quick, rough estimates, it is not suitable for tasks needing high precision. The digital lines can be thick, and aligning the phone's edge perfectly is difficult.
