If you do not have a ruler but you need a rough estimate of an object's length in centimeters, you can use any object that is known to have a width that roughly equals 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 CDs or DVDs stacked together, the thickness of a standard notepad, and the radius of a U.S. penny. Make sure that the entire item fits on the paper. Mark its starting edge with a pencil or pen. The paper needs to be light in color so that you can clearly see the marks being made. Line up one edge of your measuring object with the starting edge of the item you are measuring. 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 its eraser or unsharpened point lies flat against the edge being measured. One side of the pencil should be flush against the starting edge of the measured item. Pick up the measuring object and re-position it so that its opposite edge now lies on the mark previously created. Make another mark on the inside edge of the measuring object. Make sure that the measuring object is flat against the side of the item being measured each time you shift its position. The item being measured must remain in the same position the entire time. Keep marking the inside edge of the measuring object until you reach the end of the item being measured. Also make sure that the ending edge is marked. When finished, lift away the measuring object and the item being measured. Count the number of gaps or spaces in between your marks. This number is a rough estimate of the number of centimeters your measured item equals. It is important that you count the gaps and not the lines/marks.
لاحظ بضعة أشياء يبلغ عرضها 1 سم تقريبًا. ضع الجسم المراد قياسه على ورقة. ضع الجسم المستخدم في القياس عند علامة البداية. غير موضع أداة القياس. كرر هذه العملية. عد الفجوات.