The thumb is the largest unit on a ruler and is represented by the longest line. Each 1-inch line is labeled with a number indicating the thumb it has on the ruler (as shown in the image above). There are always 10 lines from one centimeter to the next centimeter. In total, there are three different line lengths on a metric ruler. Now that we`ve seen how to read a ruler in inches, let`s discuss how to read a ruler in cm. Example: You are trying to measure the length of your index finger. The ruler arrives at the seventh line after 3 inches. This would mean that your finger is 3 7/16 inches long. Also note that 30 cm does not directly correspond to 12 inches, although they are often placed on the same ruler! The truth is that there are tons of times in life when you need to know how to read a rule. And if you don`t know how to read a rule, you may suffer the consequences. For example, what if you make two parts of something that don`t fit together because one is shorter or longer than it should be? Or what if you mess up a science experiment because you didn`t read the measurement of a piece of string that you cut accurately? Let`s start by seeing how to read a ruler in inches. If you`re American, this is the measurement you`re probably more familiar with than centimeters, which are sometimes included on your standard 12-inch or 1-foot ruler (we`ll see how to read a ruler in cm in the next section). For example, if you want to make something from construction paper, you`ll probably need to use a ruler to measure how much material you`d need.

Or if you want to frame a photo you have? In this case, you may need to measure the image to see what kind of frame it might fit into. An English ruler provides incremental measurements in inches, with each inch divided into smaller fractions. A metric ruler provides incremental measurements in centimeters, with each centimeter divided into millimeters. Often you will find English and metric measurements on the same ruler (English along one edge and metric along the other edge). The standard metric ruler is 30 cm long. Each centimeter is labeled with a number to indicate the measurement to which it refers. You can see thumbs on the other side of your metric ruler. In this case, read the instructions above to learn how to read a ruler in inches.

The second largest unit on a ruler is the 1/2 inch, represented by the second longest line. These are usually not labeled, but may be on certain rulers (in this case, you will see numbers like 1 1/2 inches, 2 1/2 inches, etc.). Example: You take out a ruler to measure the width of your nail. The ruler stops at 1 cm, which means that your nail is exactly 1 cm wide. While we provide images to help you follow our instructions, we recommend pulling out your own ruler or tape measure so you can track in real time. The smallest unit a metric ruler can measure is 1 mm or 0.1 cm. These are the smallest lines in the ruler, that is, those between the whole centimeter and 1/2 centimeter: each inch is divided into 16 lines, which means that the distance between each line is 1/16 inch long – this is the smallest length you can measure with a ruler. (Note that some rulers only go down to 1/8-inch lines, while others go down to 1/32-inch lines.) Example: You measure the length of a strand of hair.

The strand arrives at the ninth line after 16 cm on the ruler. This would mean that the strand is 16.9 cm long (i.e. 16 cm + 9 mm). Align your metric ruler with the object you want to measure, with one end of the object aligned to point 0 of the ruler. Example: If you were to measure the length of a sheet of computer paper, the sheet of paper would reach the 11-inch mark on your ruler, indicating that it is exactly 11 inches long. Determine the English and metric equivalents by comparing the measurements with both sides of the ruler. For example, if a shelf width is 4.5 inches, look directly through the ruler at the metric edge of the ruler and note this point. Calculate the centimeter measurement of the same shelf by counting the centimeters of the same end of the ruler you used to measure in inches (the “0” point on the ruler is opposite for English and for the metric – always on the left when you hold the ruler and look at the numbers you measure with). If you count from the right end of the metric ruler labeled 30.5 cm (the “0” end for the English side), you will notice that 4.5 inches equals 11.5 cm.

Look closely at the English side of the rule. A ruler is 12 inches long, with thumb lines along the edge of the ruler (1 is on the far left and 12 is on the far right, with each number in between in numerical order). The inch-count lines are the longest lines along the edge of the ruler. Halfway between each customs line is a slightly shorter line indicating half of the customs point between each inch. Each half-inch has lines that divide it in two to indicate each quarter-inch dot between each inch. The quarter-inches have lines halfway between them to also indicate the eighth-inches. You can tell it`s a metric ruler because it`s divided into 30 evenly spaced sections and has “cm” written on it (ignore the thumbs below).