How to Use a Ruler

Four Methods:Recognizing the Different Types of RulersReading a Standard Unit RulerReading a Metric RulerMeasuring an Object Using a Ruler

A ruler is one of the most common measuring instruments. It comes in many sizes and shapes, depending on what it is needed for. The yardstick is a long ruler (3 feet long), and a measuring tape is yet another type of ruler, made of flexible cloth or metal tape. Each may look different, but are used essentially the same way. Rulers and other measuring tapes might come in both standard and metric units. It is important to know the difference between these types of measurement. This article addresses types of rulers and similar measuring tools, how to read a ruler, and using a ruler.

Method 1
Recognizing the Different Types of Rulers

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    Understand what a ruler is. A ruler is a measuring stick marked with units for measuring along its edge. [1]
    • These can be made of plastic, cardboard, metal, or fabric. marked units for measuring length along its edge.
    • These can be for either English (inches) or metric (centimeters) units of measurement.
    • In the U.S. and the UK, a student's rule is from 12 to 36 inches, or from one to three feet long. Different fractions of inches or centimeters are used to make measurements more accurate.
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    Learn what a seamstress' tape is. This is a soft fabric tape, also marked with numbers representing inches or centimeters. [2]
    • This can be wrapped around a person's torso, to measure chest, waist, neck, and other sizes for sewing clothing.
    • It may be used for measuring length, such as inseams and sleeves of garments.
    • Using these to measure 3-dimensional objects that are curved is best.
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    Know what a carpenters ruler is. These are about 6 feet long and can be folded to fit into a tool pouch or pocket. [3]
    • These are also called "stick rules".
    • Typically, these are made up of 8 inch segments.
    • They are scaled in metric units and foot and inch measures, and fractions are marked to 1/16 inch.
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    Find a tape measure and look at it. Also called measuring tapes, these are flexible metal or fiberglass tapes. [4]
    • These have a spring to rewind them into a case.
    • They are also rolled on a spool in lengths of 100 meters (or 330 feet) and longer.
    • Most measuring tapes have one side for standard and metric units.
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    Know what an architect's scale is. These are not actual lengths of measurement but will give distances to scale from a size ratio. [5]
    • These are "scale" rulers, with special marks representing a size ratio.
    • For example "1 inch equals 1 foot".
    • These are used for drawing precisely scaled blueprints and building plans.

Method 2
Reading a Standard Unit Ruler

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    Learn how standard units work. Standard units are based on feet and inches. [6]
    • The inch is the basic unit in standard measurement.
    • There are 12 inches in a foot.
    • Most rulers are 12 inches long.
    • Longer rulers, which are 3 feet long (or 36 inches long) are called yardsticks.
    • Most countries don't use this unit of measurement any longer, preferring the metric system.
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    Find the inches unit on your ruler. These are larger lines next to large numbers on your ruler. [7]
    • The distance between one of these larger lines and the next is one inch.
    • Most student rulers can measure up to 12 inches at a time.
    • You will want to measure accurately, so you will have to know more than just where the inch markers are.
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    Find the fraction of an inch markers. These delineate different fractions of an inch to help you measure as accurately as possible. [8]
    • The smallest lines in between inch markers on a ruler represent 1/16 of an inch.
    • The next largest lines represent 1/8 of an inch.
    • The next largest lines show 1/4 inches.
    • The longest line between inch markers shows 1/2 an inch.
    • You will want to measure as closely an accurately to a fraction of an inch to get a true measurement of an object.

Method 3
Reading a Metric Ruler

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    Understand what metric units are. These are the units of measurement used in the metric system. [9]
    • The larger unit of measurement in the metric system is the meter. This is close in size, but not exactly, a yard.
    • The main units of measurement in the metric system are centimeters.
    • There are 100 centimeters in a meter.
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    Find the centimeter lines on a ruler. These are the lines that have a long line with a number beside it.
    • Centimeters are smaller than inches. There are 2.54 centimeters per inch.
    • The distance between two centimeter lines is one centimeter.
    • Most standard rulers have 30 centimeters on them.
    • Meter sticks have 100 centimeters.
    • The abbreviation for centimeters is cm.
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    Learn to read the smaller units. The smaller units on a metric ruler are called millimeters. [10]
    • The abbreviation for millimeters is mm.
    • There are 10 mm in a centimeter.
    • Therefore, 5 mm is half of a centimeter.
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    Remember that all measurements in metric are in units of 10. This is an easy trick to remember for measuring in metric. [11]
    • There are 100cm in a meter.
    • There are 10 mm in a cm.
    • The millimeter is the smallest unit of measurement on most metric rulers.

Method 4
Measuring an Object Using a Ruler

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    Measure with a ruler or tape measure. Find an object or distance between two points you want to measure.
    • This can be a length of wood, string, or cloth, or a line on a sheet of paper.
    • Rulers and yardsticks are better to use on hard flat surfaces.
    • If you are measuring a person for clothing it is best to use a flexible tool like a seamstress' tape.
    • Long distances can be measured using a measuring tape.
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    Place the zero end of your rule at the end of your object. This will usually be on the left side. [12]
    • Make sure the end of the ruler is flush with your object.
    • Use your left hand to hold it in place.
    • Use your right hand to adjust the other end of the ruler.
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    Move to the opposite side of the object you are measuring. You will now read the ruler to see how long the object is. [13]
    • Read the last number on your ruler that is alongside the object. This will indicate the "whole unit" length of the object, example: 8 inches.
    • Count the number of fraction marks (dashes) the object you are measuring goes beyond the last whole number.
    • If your ruler is marked in 1/8 inch increments, and you are 5 marks past the last whole unit number, you will be 5/8 inches beyond the 8, and your length will be read "8 and 5/8 inches'.
    • Simplify fractions if you are able. For example, 4/16 of an inch is the same as 1/4 inch.
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    Use a metric or decimal rule with a metric ruler. You will be reading measurements in units of 10, following the metric system. [14]
    • Read the larger hashmarks as centimeters. Go to the nearest centimeter line. That will indicate the "whole unit" length. For example, 10 centimeters.
    • In the case of a metric rule marked in centimeters (cm), read the intermediate marks as millimeters (mm).
    • Read how many intermediate marks go past your whole unit measurement to the edge of the object. For example, if you measured an object that was 10cm plus 8mm, your measurement would be 10.8cm.
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    Use a tape measure to measure between objects, for instance, walls. A retractable steel measuring tape would work best for this.
    • Slide the zero end of the tape against one wall, or have a helper hold it, then pull out enough tape to reach the opposite wall.
    • Here, you should have two sizes of numbers, the larger for feet (or meters), the smaller, for inches (or centimeters).
    • Read the feet (or meters) first, inches (or cm), then fractions thereof.
    • Example, a distance may read "12 feet, 5 and 1/2 inches".
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    Use your 12 inch rule (or similar instrument, like a yardstick) to draw a straight line. You can also use rulers as straight edges in art or geometry.
    • Lay it down on the surface you are drawing on, and lay your pencil point along the edge of the rule.
    • Use your ruler as a guide for a straight edge.
    • Keep holding the ruler steady to get the straightest line possible.


  • These are the types of rulers that are usually used most often.
  • They can be wood, or plastic. and generally used when doing homework or in general daily usage for drawing a line, or measuring a line.
  • Play the "measuring game" here [[1]] to learn about the markings on a simple ruler.

Article Info

Categories: Stationery