To convert 20.8 millimeter to inch, multiply by the conversion factor 0.039370. The calculation is 20.8 x 0.039370 = 0.818896 inch.

20.8 millimeter equals exactly 0.818896 inch. For practical purposes, this is often rounded to 0.8189 inch.

Objects measuring approximately 20.8 millimeter include the diameter of a CR2032 Lithium Coin Cell Battery (20.0mm), the diameter of a US Nickel coin (21.21mm), and the internal diameter of a 20mm metric socket (20.0mm).

Converting millimeter to inch is useful for international manufacturing and trade, especially when dealing with countries like the United States that primarily use imperial units. It ensures compatibility of parts, facilitates communication in global supply chains, and is essential for integrating components designed under different measurement standards.

A simple memory aid is to remember that 1 millimeter is slightly less than 0.04 inch. For 20.8 millimeter, you can quickly estimate it as 'a bit over 0.8 inch.' Visually, think of a US Nickel coin (21.21mm) as a close reference for this dimension.