mm to inches | how to convert easily

This video demonstrates two methods how to convert from mm to inches. One that you will use when a calculator is available or you need accuracy, and another one, that can be useful when a calculator is unavailable or all that you need is only a quick approximation.

The accurate conversion from mm to inches is defined with this equation: 1 inch equals 25.4 mm. This is the conversion rule. So, getting inches from mm is rather straightforward. Simply, multiply with 25.4. For example: 4 inches make 4 times 25.4 equals 101,6 mm.

To get inches from mm, we must do the reverse operation. Reverse of multiplication is division of course, so we must divide millimeters by 25.4. For example, 100 mm make…. 100 divided by 25.4 equals 3.94 inches, approximately. As you can imagine, a calculator is rather necessary to perform the division accurately, at least for most people. But, what if you are in hurry or you are driving, or your smartphone is out of battery?

Well, there is another easier method, which is slightly less accurate. Remember the conversion rule? If we round it to 1 inch equals 25 mm, we introduce a small error but, we find out that now 4 inches make 100 millimeters exactly. Or, that 1 mm equals four hundredths of an inch which is very convenient. This is the trick: instead of dividing by 25, we multiply mm with 4 and then divide by 100. Far more easy operations to do manually compared to division. Let’s see an example… if we have say 120 mm, and we need to convert to inches, first, we multiply with 4, which gives 480, then divide by 100, and finally get 4.8 inches. The accurate conversion gives 4.72 inches, in comparison. Quite acceptable.

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