How to Read an Inch Ruler or Tape Measure

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How to Read a Ruler

Two Methods:

There are two types of rulers: the inch ruler with fractional division, and the metric ruler with decimal division.Reading a ruler can seem daunting with all the little lines, but it is quite simple. Once you understand the basics listed below, you'll have no trouble at all taking measurements with either type of ruler.


Reading an Inch Ruler

  1. Get an inch ruler.You will know it is an inch ruler because it will have 12 lines that denote inches on the ruler. 12 inches equals 1 foot (0.305 m). Each foot is broken down into inches. Each inch is broken down into 15 smaller marks, equaling 16 marks in total for each inch on the ruler.
    • The longer the line on the surface of the ruler, the bigger the measurement is. Ranging from 1 inch to 1/16 of an inch, the lines decrease in size as the unit of measurement does.
    • Make sure you read the ruler from left to right. If you are measuring something, align it with the left side of the zero mark on the ruler. The left side of the line where the object ends will be its measurement in inches.
  2. Learn the inch marks.A ruler is made up of 12 inch marks. These are typically the numbered marks on the ruler and are denoted by the longest lines on the ruler. For example, if you need to measure a nail, place one end directly on the left side of the ruler. If it ends directly above the long line next to the large number 5, then the nail is 5 inches long.
    • Some rulers will also denote 1/2 inches with numbers, so make sure you are using the largest numbers with the longest lines as your inch markers.
  3. Learn the 1/2 inch marks.The 1/2 inch marks will be the second longest lines on the ruler, half as long as the inch marks. Each 1/2 inch mark will come midway between each inch number because it is half of an inch. This means that marks directly between the 0 and 1 inch, 1 and 2 inches, 2 and 3 inches, and so on across the ruler, are the 1/2 inch marks. In total, there are 24 of these marks on a 12 inch ruler.
    • For example, place the ruler against a pencil with the eraser at the far left of the ruler. Mark where the tip of the pencil lead ends on the ruler. If the pencil point ends at the shorter line halfway between the 4 and 5 inches marks, then your pencil is 4 and 1/2 inches long.
  4. Learn the 1/4 of an inch marks.halfway in between each 1/2 inch line, there will be a smaller line that denotes a 1/4 of an inch. In the first inch, these marks will mark 1/4, 1/2, 3/4, and 1 inch. Although the 1/2 inch and 1 inch marks have their own lines, they are still part of the 1/4 of an inch measurements because 2/4 of an inch equals half an inch and 4/4 of an inch equals 1 inch. There are a total of 48 of these marks on a 12 inch ruler.
    • For example, if you measure a carrot and the tip falls on the line halfway between the 6 1/2 and 7 inch lines, the carrot is 6 and 3/4 inches long.
  5. Learn the 1/8 of an inch marks.The 1/8 of an inch marks are the smaller marks found directly in between the 1/4 of an inch marks on the ruler. Between 0 and 1 inch, there are marks that denote 1/8, 1/4 (or 2/8), 3/8, 1/2 (or 4/8), 5/8, 6/8 (or 3/4), 7/8, and 1 (or 8/8) of an inch. In total, there are 96 of these marks on a 12 inch ruler.
    • For example, you measure a piece of fabric and the edge falls on the 6th line after the 4 inch mark, which is directly in between the 1/4 of an inch mark and the 1/2 inch mark. This means that your fabric is 4 and 3/8 inches long.
  6. Learn the 1/16 of an inch marks.The small lines halfway between each 1/8 of an inch denote 1/16 of an inch. These are also the smallest lines on the ruler. The very first line on the left hand side of the ruler is the 1/16 of an inch mark. Between 0 and 1 inch, there are marks that denote 1/16, 2/16 (or 1/8), 3/16, 4/16 (or 1/4), 5/16, 6/16 (or 3/8), 7/16, 8/16 (or 1/2), 9/16, 10/16 (or 5/8), 11/16, 12/16 (3/4), 13/16, 14/16 (or 7/8), 15/16, 16/16 (or 1) of an inch. There are a total of 192 of these lines on the ruler.
    • For example, you measure a flower stem and the end of the stem falls on the 11th line after the 5 inch mark. The flower stem is 5 and 11/16 inches long.
    • Not every ruler will have the 1/16 inch mark. If you plan on measuring things that are small or you need to be extremely accurate, make sure the ruler you use has these marks.

Reading a Metric Ruler

  1. Get a metric ruler.A metric ruler is based on the International System of Units (SI), sometimes called the metric system, and is divded into either millimeters or centimeters instead of inches. Rulers are often 30 centimeters long, which are designated by large numbers on the ruler. Between each centimeter (cm) mark, there should be 10 smaller marks called millimeters (mm).
    • Make sure you read the ruler from left to right. If you are measuring an object, align it with the left side of the zero mark on the ruler. The left side of the line where the object ends will be its measurement in centimeters. This way the line thickness will not affect the measurement.
    • Unlike with the English ruler, the measurements for the metric ruler are written in decimals instead of fractions. For example, 1/2 a centimeter is written as 0.5 cm.
  2. Learn the centimeter marks.The large numbers next to the longest lines on the ruler denote the centimeter marks. A metric ruler has 30 of these marks. For example, place the bottom of a crayon on the far left side of the ruler to measure it. Note where the tip falls. If the crayon ends directly on the long line next to the large number 14, your crayon is exactly 14cm long.
  3. Learn the 1/2 of a centimeter marks.halfway between each centimeter, there is a slightly shorter line that denotes 1/2 of a centimeter, or 0.5cm. There are a total of 60 of these marks on a 30 cm ruler.
    • For example, you measure a button and the edge ends on the fifth line right between the 1 and 2 centimeter marks. Your button is 1.5cm long.
    • For example, to measure 0.6 cm, count one thick line (5 mm) and one thin line (1 mm).
  4. Learn the millimeter marks.Between each 0.5cm line, there are four additional lines that denote the millimeter marks. There are a total of 10 lines per centimeter, with the 0.5cm line acting as the 5 millimeter mark, making each centimeter 10mm long. There are 300 millimeter marks on a 30 cm ruler.
    • For example, if you measure a piece of paper and it ends on the 7th mark between the 24 and 25 centimeter mark, it means your object is 247mm, or 24.7cm, long.

Community Q&A

  • Question
    What is 55.5? Is that larger than 55 1/4?
    wikiHow Contributor
    Community Answer
    The 55.5 is larger than 55 1/4. the .5 on the 55.5 would equal 1/2. Therefore, 55.5 is equal to 55 1/2 which is 1/4" larger than 55 1/4.
  • Question
    Can I learn to read a ruler in one day?
    wikiHow Contributor
    Community Answer
    Yes, but it really depends on what type of ruler you want to learn as well as how fast you pick up new material
  • Question
    What does it mean when mm is shown just beside the 0 in a ruler?
    wikiHow Contributor
    Community Answer
    Each small line represents 1mm. Therefore, the first line past the big number (for instance 25) will represent 25.1cm or 251mm.
  • Question
    Where can I find the centimeter markers on a ruler?
    wikiHow Contributor
    Community Answer
    The centimeters side is usually the part of the ruler where the markers are shorter and closer together. It reads cm, and has more numbers.
  • Question
    Why there is a space at the beginning of a ruler?
    wikiHow Contributor
    Community Answer
    Some lower quality rulers have spaces at the beginning to make the rulers easier to use. Higher quality rulers are often made of non-elastic materials like steel or aluminum, and their markings start without any space.
  • Question
    What does 0.75 cm look like?
    wikiHow Contributor
    Community Answer
    It's in the middle between the 7th and 8th millimeter lines in a centimeter. In other words, it ends in the middle of the second half of a centimeter.
  • Question
    Is 7/8 larger than 1 inch?
    wikiHow Contributor
    Community Answer
    7/8 is smaller than 1 inch. 1 inch represents a whole, while 7/8 represents 7 parts of a whole (8 parts).
  • Question
    Is 12 inches longer than a foot? I am feeling stumped by this.
    wikiHow Contributor
    Community Answer
    They're the same 12in = 1ft.
  • Question
    Is 5.5 mm closer to a half inch or a quarter inch?
    wikiHow Contributor
    Community Answer
    A quarter inch. 6 mm is almost a quarter inch, whereas half an inch looks closer to 12-13 mm, so 5.5 would be close to a quarter of an inch.
  • Question
    Why are there five holes in my 12" ruler?
    wikiHow Contributor
    Community Answer
    So you can put the ruler in a 3- or 5-ring binder to use in school or in an office environment.
Unanswered Questions
  • How do I read millimeters on a ruler?
  • Why can't I use a regular tape measure to figure out my ring size?
  • What about if I'm trying to find out 2 inches or 3 inches?
  • Where is 2/3" on a ruler?
  • How many millimeters are in an inch?
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Quick Summary

To read a metric ruler, look at the long lines on the ruler that are numbered 1-30, otherwise known as the centimeter marks. The distance between them is equal to 1 centimeter. To read an English ruler, start by looking at the longest lines on the ruler that are numbered 1-12. These lines are the inch marks, and the distance between each line is equal to 1 inch.

Did this summary help you?
  • Learning to read a ruler takes practice, especially converting the numbers in the measurements. Just remember to practice using your ruler and you'll get better at it.
  • Make sure you always use the correct side of the ruler for the task at hand. You don't want to get the centimeters and the inches mixed up or your measurements won't be correct. Remember that there are 12 large numbers on an English ruler and 30 numbers on the metric ruler.

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303 votes - 71%
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71% of people told us that this article helped them.
Views: 1,555,690


Jun 2

"Helpful when you can double-check different lengths."


May 4

"This is very simple and clear. This is standing between me and getting a job offer. Before now I had very fairidea, but right now I can even teach the measurements. Thanks."

Ellen L.

Aug 23, 2019

"This is the best explanation of reading a ruler I have ever read. As a woman with learning disabilities growing upin the 60s, the fact that I could not read a ruler got overlooked. I finally got it from your tutorial after all of these years. No one ever broke it down and worked backwards to explain it - that's why I couldn't get it. Thank you!"

McKya Bramlett

Aug 14, 2019

"I have never really known what all of the marks meant just the basic 1/4", 1/2", 3/4", etc. I didn'twant to ask my husband for help, I wanted to figure it out on my own. So I got online and asked Cortana for her help, and she lead me to your site. I know more now about a ruler or tape measure than I ever have before."
Rated this article:


Dec 9, 2019

"How it was explained, the article mentioned it step by step, and explained everything from mm, cm, in. I reallyfind this article helpful, I had to save it so I can return to it, as I will be studying it each day. Thank you, I will keep studying."


Feb 10, 2019

"I've always being weak in math, and I've learned a lot today. I'm very happy to have learned so much, especiallywhere all the centimeters and millimeters on the ruler are located. Thanks for the great lessons on how to read a ruler."

Madison Chambers

Aug 30, 2019

"This has helped me a lot. In school I'm in a masonry class and I was having problems reading and remembering all ofthe tic marks. Now when I go to lay down the measurements on my work, I don't have to ask my teacher about it."
Rated this article:

Nhan Le

Sep 22, 2019

"I came from another country that uses a metric system. When I came here I had to learn a different measurementsystem. Sometimes I'm confused. This article is so useful for me. "

Kat Lebron

Jun 11, 2019

"I make crafts and sometimes I don't have the appropriate ruler, this article helped me learn basically all theparts of a measuring tape. So now there's no holding back!"
Rated this article:

Onyx Chi

Sep 25, 2019

"I'm working on my math and needing to use centimeters, but I only have an inch ruler. So with this alongside acentimeter to inch converter, it has really helped."

Sandy Stratton

Apr 11, 2019

"Very helpful and informative. I didn't even know that metric means reading from left to right. Wow! No wonder Ihave had such conundrums with measurements."

Maria Abdalla

Aug 16, 2019

"I have always had trouble reading a ruler, but this article really broke it down for me in a way I understood andwould remember. Thanks!"
Rated this article:

Lytta Grey

Aug 26, 2019

"The pictures really helped because I'm a visual learner and I also have a photographic memory. Seeing it helps meto learn it faster."

Rhonda Junius

Mar 1

"I am learning how to make a book for myself. While doing this you need to understand the ruler, as everything needsto be measured."
Rated this article:

John O'Donnell

Aug 18, 2019

"It helped me understand something that had baffled me my entire life, I am self taught mostly. I like learningthings for myself."
Rated this article:

Sharon Campbell

Aug 15, 2019

"Rulers have always strained my brain. So many measurements, yikes! This clear breakdown for ruler dummies wasgreat! Thanks!"

Stephanie Scott Mashburn

Jan 22

"I need to learn how to read a ruler for the job I may be getting. This helps me out a great deal. Thanks a bunch!"

Ollie Harley

Jul 25, 2019

"Had senior moment! Needed a fast refresher class. Thanks to wikiHow article I am able to finish my project."
Rated this article:

Paula Brown

May 26, 2019

"For years, I couldn't quite get measurements on the ruler. This has broken it down for me. Thank you."
Rated this article:

Lola Lili

Apr 26, 2019

"This is great! I have learned more from this relative to what I was taught in class! Thank you!"

Mary Adams

May 21, 2019

"Looking for 3 1/5, but it isn't there, so it must be 3 1/4. The marks are even numbers."
Rated this article:


Apr 4, 2019

"Everything helped! Very easy to understand and learn how to use each measurement."

Jason Lester

Aug 25, 2019

"This helped me because we are doing a lot with rulers in my robotics class. "
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Mar 25

"I have had to see this a couple times to really get it, but now it's stuck!"


Dec 13, 2019

"The illustrations with pictures to help understand the written details."


Sep 13, 2019

"This helped me perfectly, please keep this site up. Thank you so much!"
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Jan 27

"This made things very easy to break down.

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Date: 01.12.2018, 04:50 / Views: 54252