How to Read a Ruler

Have you ever had to use a ruler only to find it difficult to read? Even though we all know what a ruler is, it can be challenging trying to figure out what all those small lines mean.
Nonetheless, these ingenious tools are everywhere! They’re used in schools, colleges, and in a wide array of professions.
Because we know the importance of learning how to read a ruler, we created this handy guide. We’ve even broken it down into imperial and metric rulers.
Honing your ruler-reading abilities isn’t only useful at school or work; it’s a must-have skill for daily life, so let’s get measuring!

How to Read a Ruler

One type regularly used in the US is the standard 12-inch ruler. Such rulers use inches, feet, and yards to measure the length of objects. They’re referred to as imperial rulers.
Another ruler type is the metric ruler, which uses millimeters, centimeters, and meters as its measurement units.
Note that the metric system is commonly used in more countries around the globe than the imperial system.
Some rulers can be available as only metric or imperial, then there are those that come with both measuring systems printed on the two edges lengthwise.
There are several types of rulers available, such as:
  • Metal or wooden rulers
  • Seamstress and measuring tapes
  • Architect and engineer scales
  • Folding rulers, aka carpenter rulers

Standard Imperial Rulers

Imperial rulers are one foot long, or 12 inches. When you put three of them together and lay them end-to-end, you get a yardstick, or 36 inches. When you reach a length of 1760 yards, you get one mile.
On almost all standard 12-inch rulers, you’ll get the word ‘inch’ printed out at the ‘0’ line. Then, you have clear markings for the numbers one to 12.
In between each of these numbers are 15 smaller markings. Half-way between each inch is the longest of these markings. It marks the halfway point.
To the left and right of this halfway point are the quarter and three-quarters markings. Then, between these are marks that start from 1/16 of an inch and go up to 15/16. This means that each inch is made up of 16 markings and each marking represents 1/16th of one inch.

Markings on an Imperial Ruler

Here’s what each of the markings stands for on an imperial ruler for starting at 0:
  • 0
  • 1/16
  • 2/16 = 1/8 of an inch
  • 3/16
  • 4/16 = 1/4 of an inch
  • 5/16
  • 6/16 = 3/8 of an inch
  • 7/16
  • 8/16 = 1/2 of an inch
  • 9/16
  • 10/16 = 5/8 of an inch
  • 11/16
  • 12/16 = 3/4 of an inch
  • 13/16
  • 14/16 = 7/8 of an inch
  • 15/16
  • 16/16 = 1 inch

Metric Rulers

Metric rulers are 30 centimeters long. They have ‘cm’ written next to the ‘0’ line and consist of 9 small markings between each centimeter. This means there are 10 millimeters in each centimeter.
Each line stands for one millimeter. The fifth marking is the longest of all nine. It marks the halfway point between every two centimeters.
In the metric system, 100 centimeters equals one meter, and 1000 meters is equal to one kilometer. There’s even a meter stick that makes measuring longer objects more manageable.

Markings on a Metric Ruler

Here’s what each marking on a metric ruler stands for starting at 0:
  • 1mm = 0.1 cm
  • 2mm
  • 3mm
  • 4mm
  • 5mm = 0.5 cm
  • 6mm
  • 7mm
  • 8mm
  • 9mm
  • 10mm = 1 cm

How to Measure Using a Ruler

Measuring objects with a ruler uses a similar approach regardless of which measuring tool you use. You also use the same basic technique whether you’re using an imperial or metric ruler.
First, you need to line up one end of the object you’re measuring with the ‘0’ mark. Next, line up the ruler with the object. Make sure they’re both aligned and parallel to one another.
The final step is to look at the number on the ruler that the other end of the object corresponds with. If it stops in-between inches, count the smaller markings.
So, let’s say you’re measuring the length of a piece of yarn on an imperial ruler. Lay them on a flat surface side-by-side.
Let’s say the yarn runs from 0 up to 5 inches and 4/16th of an inch. This means the yarn measures 5 1/4 inches.
Now, let’s take the same piece of yarn and measure it with a metric ruler. Lay the piece of yarn at the ‘0’ mark. The length of the yarn will come out to about 13 centimeters and three millimeters, or 13.3 centimeters long.
If you’re measuring or drawing lines on a piece of paper, it can be useful to draw a small dot next to the measurement. This is especially helpful when you’re using the metric ruler since the lines are close together.

Imperial vs Metric Rulers

If your ruler has numbers running on both sides, then you have both an imperial and a metric ruler. The imperial ruler is the side with the larger marks. It’s the one that has wider gaps between each marking.
The other side with the lines running close together is the metric system. As we mentioned before, most metric rules will go up to 30 centimeters, which is the equivalent of 12 inches.
We’ve put together a quick overview to give you a clear idea of how inches and centimeters compare.
  • 1 inch = 25.4 millimeters
  • 1 foot = 30.5 centimeters
  • 1 yard = 0.9 meters
  • 1 mile = 1.6 kilometers


Knowing how to read a ruler is one of those basic life skills, like learning to ride a bike or crossing the street while chewing gum. It has nothing to do with age or profession, but it’s definitely going to come in handy in many aspects of your life.
We know how tricky it can be in the beginning trying to decipher the meaning behind those lines and markings. Yet, once you know what you’re doing, using any type of ruler becomes easy as pie.