How to Read a Ruler In Inches and Centimeters

Rulers are highly important tools that help you figure out the lengths of things. But as simplistic as they are, many people still experience difficulty trying to measure tiny objects with them. After all, there are so many lines that denote so many things, so how do you figure out what means what?

Worry not. In this guide, I will show you exactly how this process is done. So, if you have a ruler on hand, whip it out and follow along as I explain how to read a ruler in inches.

What Is a Ruler?

First things first, let’s talk about what rulers are.

A ruler is a measuring tool made of wood or plastic. Usually, one side will have lines that denote inches, and on the other side are lines that denote centimeters. Rulers are similar to yardsticks but typically only measure 12 inches long.

Rulers can also be used to draw straight lines that are as long as the length of the tool. Nearly everyone—from students to professional engineers and architects—will need to use a ruler sometime in their field.

Importance of Reading a Ruler

While students and professionals will use rulers almost on a daily basis, reading a ruler is a helpful life skill.

Have you ever wanted to measure the dimensions of a quart-sized Ziploc bag? Or maybe you’re looking for a more accurate way to measure 1 cubic foot? A ruler can come in handy for both of these examples and much, much more.

But what are the consequences of not knowing how to read a ruler? Well, if you’re into arts and crafts, you could end up with a yard of fabric that’s longer than you originally hoped for. For the DIY woodworking aficionados out there, you’ll most likely become exasperated when you discover 2 joints don’t fit together seamlessly. If only you measured your materials beforehand…

So, it’s pretty clear that measuring things is an important part of everyday life.

How to Read a Ruler in Inches

Now, it’s time to get to the crux of the matter—how to read a ruler in inches.

The largest numbers on the standard imperial side of a ruler denote inches, starting from 0 all the way up to 12 (1 foot).

If you take a closer look, you’ll find smaller markings between each inch. Those markings show fractions of an inch. Most rulers will have markings that denote 1/16th or 1/8th of an inch. There are also special rulers that show 1/32nd of an inch, but these are mainly used by professionals who can’t afford to make the slightest measurement error.

For now, let’s focus on the markings between the 0 and 1-inch lines with 1/16th-inch markings. Between them, you’ll find 15 markings of various lengths. From longest to shortest, these markings indicate the following:

• Longest—1 inch
• 2nd longest—1/2 inch
• 3rd longest—1/4 inch
• Shortest—1/16 inch

Starting from left to right, the markings between the 0 and 1-inch lines are as follows:

Examples of How to Read a Ruler in Inches

Allow me to demonstrate how you can use a ruler to measure something in inches and fractions of an inch.

Let’s say you have 3 pieces of string on hand and want to measure their lengths in inches. Place the end of each string on the 0-inch mark and stretch toward the opposite end of the ruler.

• The first piece of string reaches the 5th marking between the 0 and 1-inch lines. This piece of string measures 5/16 of an inch long.
• The second piece of string reaches the 12th marking between the 0 and 1-inch lines. This piece of string measures 12/16 of an inch long (simplified to ¾ of an inch).
• The third piece of string reaches the 3rd marking after the 1-inch line. This piece of string is 1 inch + 3/16 of an inch long (1-3/16 inches).

At first, you may struggle to simplify the different fractions in your head (4/16 à ¼, 8/16 à ½, etc.), but the more frequently you use a ruler, the easier it becomes.

How to Read a Ruler with Irregular Fractions

Most people will use rulers to measure 1/16, 1/8, ¼, ½, or whole inches. However, there may come a time when you want to measure inches in thirds, fifths, sevenths, or tenths. This might sound challenging, but believe me—it’s not.

Below, I will provide a brief chart explaining the equivalents of each 1/16th tick mark in decimals:

To use this table, you need to first figure out the decimal figure of what you want to measure and the decimal figure of each tick mark on the ruler (provided above).

For example, let’s say you want to figure out what 2/9th of an inch is. 2 divided by 9 is equal to 0.222. Compare this figure with the third column in the chart above and see which markings are closest to it. In this example, 0.222 is closest to the third (3/16) and 4th (4/16 or ¼) tick lines. So, 2/9 of an inch should be somewhere between those lines.

Let’s use another example. How do you locate 3/10th of an inch? 3 divided by 10 equals 0.3, which is closest to the 4th (4/16 or ¼) and 5th (5/16) lines. 3/10 of an inch will be somewhere between them.

You can use this method to calculate anything, including 1 millionth or billionth of an inch!

Where is 1″ on a ruler

The 1-inch mark on a ruler can be found after counting 16 tick marks starting from the 0-inch point. Alternatively, you can look at the whole inch following the 0 inches. The line should be just as long as the 0-inch line.

Where is 1/2″ on a ruler

The ½-inch mark on a ruler can be found in the middle of the 0 and 1-inch lines. It is denoted by the second-longest line.

Where is 1/3 inches on a ruler

Calculating inches in thirds (1/3 or 2/3) can be a bit tricky. The 16 tick marks between each whole line mark cannot be divided into thirds without using a bit of imagination.

1/3 is equal to 0.33, which is found between the 5th (5/16 or 0.3125) and 6th (6/16, 3/8, or 0.375) lines.

Where is 1/4″ on a ruler

The ¼-inch or quarter-inch mark on a ruler can be found between the 0 and the half-inch mark (the 8th tick line).

Where is 1/6 inches on a ruler

Similar to 1/3rd of an inch, you will have to estimate where 1/6th of an inch is located. 1/6th equals 0.1667, which using the decimal chart provided above, should be somewhere between the second (2/16) and third (3/16) ticks.

Where is 1/8″ on a ruler

While counting in eighths can be tricky, a standard ruler makes it easy since the space between each tick mark denotes 1/8th of an inch in distance. To find the 1/8th-inch mark, simply look for the second tick mark (2/16 or 1/8) following the 0-inch line.

Where is 1/16″ on a ruler

Calculating even smaller fractions is even more difficult than measuring in eighths. The good news is that standard rulers have 1/16th-inch lines between each whole inch number. So, 1/16th of an inch on a ruler will be the first tick mark following the 0-inch line.

Where is 2/3 inches on a ruler

If you know where 1/3rd of an inch on a ruler is, you should be able to estimate where 2/3rd is. Simply multiply the distance of 1/3 by 2 to get the final count. However, to be more precise with your measurements, you can use the table provided above.

2/3 is equal to 0.667, which is between the 10th (10/16, 5/8, or 0.625) and 11th (11/16 or 0.6875) marks.

Where is 2/5 inches on a ruler

One common mistake people make when using a ruler is that they think each tick mark is the same as 1/10th of an inch. As explained throughout this article, each tick mark on a standard ruler is actually 1/16th of an inch. So, finding 2/5 of an inch can be a bit tricky.

2/5 is the same as 0.4, which is pretty close to 0.5 (1/2 or 8/16). To be more precise with your measurements, 2/5 of an inch should be found between the 6th (6/16, 3/8, or 0.375) and 7th (7/16 or 0.4375) tick marks.

Where is 3/4 of an inch on a ruler

¾ of an inch on a ruler will be precisely between the ½ and 1-inch lines. Remember that the second-longest lines denote half inches and the third-longest lines are quarter (1/4) inches. Simply add the distance between the second-longest and following third-longest lines to reach ¾. Alternatively, you can count 1/4th of an inch back from the 1-inch line.

Where is 3/8 of an inch on a ruler

Each 2 tick marks on a ruler denotes 1/8th of an inch. So, 3/8 would equal 6 marks starting from the 0-inch line. Another way to look at it is to count 2 tick marks back from the half-inch mark since half an inch equals 4/8.

Where is 3/16 of an inch on a ruler

Whenever you want to measure 16th of an inch, all you have to do is take a look at the individual tick marks. Each tick is 1/16th of an inch, so 3/16 would be 3 ticks from the right of the 0-inch line.

Where is 3/32 inches on a ruler

Things can get a bit complicated if you want to measure in the 32nd of an inch. First, you should know that the standard ruler is designed to measure just fractions of an inch in 16ths. Luckily, you can figure things out pretty easily, especially if you’re looking for even fractions of 32nds (e.g., 4/32, 8/32, 18/32) simply by dividing them by 2 (2/16 or 1/8, 4/16 or ¼, 9/16, respectively).

3/32 of an inch would be between 2/32 (1/16) and 4/32 (2/16). Another way to look at it is that 3/32 is equal to 1.5/16 or the halfway mark between the 1/16 and 2/16-inch ticks.

Where is 5/8 of an inch on a ruler

To measure eighths on a ruler, simply look at every 2 1/16th-inch tick mark. For instance, the first 2 would equal 1/8, the following 2 would equal 2/8 (1/4), and so on, starting from the 0-inch line.

5/8 of an inch would be 2 ticks after the ½-inch line. You could also convert it to 10/16 and count 10 ticks after the 0-inch line or 6 ticks back from the 1-inch line.

Where is 7/16 of an inch on a ruler

Do you remember how ½ is the same as 8/16? If so, then finding the 7/16th-inch tick mark should be fairly simple. Just measure 1 tick (1/16th of an inch) beyond the half-inch line. Alternatively, you could count 7 tick marks from the 0-inch line.

Where is 7/8 of an inch on a ruler

7/8 of an inch is incredibly close to a full inch. However, since each tick represents 1/16th of an inch, you’ll need to count 2 ticks back from the 1-inch line to get to 7/8ths. You could also could 14 ticks from the 0-inch line (7/8 equals 14/16).

Where is 11/16 of an inch on a ruler

Counting in 16ths of an inch is simple on a standard ruler since each tick line represents 1/16th of an inch. So, 11/16th of an inch would equal 11 ticks after the 0-inch line or 5 ticks before the 1-inch line. You can figure this out quickly by looking for the half-inch line (the second-longest line in between the 0 and 1-inch lines) and counting 3 ticks to the right (1/2 or 8/16 plus 3/16 equals 11/16).

Where Are Inches On a Ruler (Summary Chart)?

How to Read a Ruler in Centimeters

If you take a look at the opposite side of the inch markings, you’ll most likely find a series of closely packed tick marks. Those tick marks represent centimeters. To use the centimeter side of a ruler, simply rotate the ruler 180°. The 0-centimeter line will be on the opposite end of the ruler, and the 30-centimeter (roughly) line will be located almost completely opposite of the 12-inch line.

You can use the centimeter side of a ruler precisely in the same way you use the inch side. The only difference is that each tick line is not equivalent to 1/16th of an inch. Instead, you’ll find large prints of integer numbers (between 1 and 30) that represent whole centimeters with 9 tick marks between them. Those smaller ticks are millimeter (10 millimeters equals 1 centimeter).

So, how do you use a ruler to read in centimeters? Carefully align the 0-centimeter mark on the edge of the object you wish to measure. Now, locate the end of the object and see which centimeter and millimeter tick mark it reaches.

Here’s a quick example of what I mean:

• A piece of string measures 9 tick marks long. That would equal 9 millimeters or 0.9 centimeters.
• A piece of string measures 4 tick marks long. That would equal 4 millimeters or 0.4 centimeters.
• A piece of string measures 17 tick marks long. That would equal 17 millimeters or 1.7 centimeters.

Alternatively, you can use the inch side of your ruler to measure an object and convert it to centimeters. The following chart will describe the millimeter and centimeter equivalents of inch fractions.