Content

• To step
• Method 1 of 4: Measure using a ruler
• Method 2 of 4: Estimate the number of centimeters using objects
• Method 3 of 4: Converting to the metric system

The centimeter is a metric (or also: metric) unit of measure. You can use most rulers for measuring centimeters. However, it is important to make sure you are using the correct units as many rulers and especially tape measures also indicate inches. If you don't have a ruler, you can use regular office supplies to estimate the size in centimeters. You can also convert other measurement units to centimeters.

To step

Method 1 of 4: Measure using a ruler

1. Find the inches on the ruler. Many rulers have two sets of numbers. You are looking for the metric sequence of numbers. This side of the ruler is labeled ${ displaystyle cm}$Understand the relationship between a millimeter and an inch. If you look closely at the ruler, you will see that every centimeter is divided into 10 parts by the shorter lines. A millimeter is one tenth of a centimeter.
   • Remember that 1 mm = 0.1 cm.
2. Align the edge of the object with the first centimeter line on the ruler. Note that the edge of the physical ruler is often misaligned with the start of the first centimeter. So make sure you place the object along the first line and not on the edge of the ruler.
   • Hold the ruler as flat as possible against the side of the object to be measured.
3. Determine the length in whole centimeter. Look at the other side of the object. Determine which point is closest to that edge. This point indicates how long the object is.
   • If the border falls on a longer centimeter line, marked with an integer, the object is that number of centimeters long. For example, if the edge of an eraser ends at the line marked 7, the eraser is 7 cm long.
   • When measuring to the nearest centimeter, look for the line closest to the edge of the object, marked with a number. This mark indicates the nearest centimeter. For example, a piece of eraser may fall halfway between the 7 and 8 cm marks. Since the eraser ends closer to the 7 cm mark, you would say that, based on the nearest centimeter, the eraser is 7 centimeters long.
4. Determine the length to the nearest tenth of an inch. Look at the last centimeter that goes to the edge of the object. Then you count the number of millimeters beyond the last whole centimeter to the edge of the object. Every millimeter is one-tenth of an inch. So, to find the length, add the number of whole inches to the tenths of an inch.
   • For example, if the edge of an eraser ends 1 millimeter past 7 centimeters, the eraser is 7.1 centimeters long.

Method 2 of 4: Estimate the number of centimeters using objects

1. Find some objects that are about 1 cm wide. If you don't have a ruler, roughly estimate the length of an object in centimeters, using an object that you know has a width that equals about one centimeter.
   • The easiest objects to use are a standard pencil, pen, or highlighter. The width of a pencil is close to 1 cm.
   • Other options include the length of a staple, the width of five stacked CDs or DVDs, the thickness of a standard scratch pad and the diameter of 10 cents.
2. Place the object you want to measure on a piece of paper. Make sure the entire object fits on the paper. Mark the first edge with a pencil or pen.
   • The paper should be light in color so you can clearly see what marks you are making.
3. Place the measurement object against the first edge. Align one edge of the measurement object with the start side of the item you want to measure.
   • For example, if you are using the width of a pencil to estimate centimeters, place the pencil perpendicular to the item being measured so that the eraser or the unsharpened side of the pencil is flush against the edge to be measured. One side of the pencil should be along the first side of the item to be measured.
4. Mark the opposite edge of the measurement object. Be careful not to move the measurement object and make a small mark against the inside edge of the measurement object with a pencil or pen.
5. Move the position of the measurement object. Now place the measurement object so that the opposite edge is now on the previously created marker. Make another mark on the inner edge of the measurement object.
   • Make sure the measurement object is flat against the side of the measurement item each time you shift the position of the measurement object. The item to be measured must always remain in the same position.
6. Repeat this process. Continue to mark the inner edge of the measurement object until you reach the end of the measurement item. Also make sure the end edge is marked.
7. Count the steps. When you are done, lift the measurement object and the item being measured. Count the number of steps or spaces between the marks. This number is a rough estimate of how many centimeters the measured object is long.
   • It is important that you count the steps and not the lines / markers.

Method 3 of 4: Converting to the metric system

1. Convert millimeters to centimeters. There are 10 millimeters in 1 centimeter. If you want to convert millimeters to centimeters, divide the number of millimeters by 10.
   • For example, if you want to convert 583 millimeters to centimeters, this goes like this: ${ displaystyle { frac {583} {10}} = 58.3}$Convert meters to centimeters. There are 100 centimeters in 1 meter. If you want to convert meters to centimeters, you have to multiply the number of meters by 100.
     • For example, if you want to convert 5.1 meters to centimeters, this goes as follows: ${ displaystyle 5.1 times 100 = 510}$Convert kilometers to centimeters. There are 100,000 centimeters in a kilometer. To convert kilometers to centimeters, multiply the original measurement by 100,000.
       • For example, if you want to convert 2.78 kilometers to centimeters, it would go like this: ${ displaystyle 2.78 times 100,000 = 278,000}$Convert inches to centimeters. In 1 inch it only goes 2.54 centimeters. To convert inches to centimeters, multiply the number of inches by 2.54.
         • For example, if you want to convert 9.41 inches to centimeters, here's how:${ displaystyle 9.41 times 2.54 = 23.9}$Convert feet to centimeters. In 1 foot goes 30.48 centimeters. So, to convert feet to centimeters, multiply the number of feet by 30.48.
           • For example, if you want to convert 7.2 feet to centimeters, you do this:${ displaystyle 7.2 times 30.48 = 219.46}$Convert yards to centimeters. A yard is 3 feet. Since 30.48 inches go into 1 foot, the number of inches in a yard is threefold: 91.44. To convert yards to centimeters, multiply the number of yards by 91.44.
             • For example, if you want to convert 3.51 yards to centimeters, this goes like this:${ displaystyle 3.51 times 91.44 = 320.96}$. So 3.51 yards is the same length as 320.96 inches.