Which metric unit is used to measure very small lengths such as foil thickness?

• A. Meter
• B. Centimeter
• C. Micrometer
• D. Millimeter

Answer: (C)

When measuring very thin objects, use a unit at the micro scale. Foil thickness is typically on the order of tens of micrometers, so expressing it in micrometers keeps the number small and intuitive. A meter is too large to describe thin films in a practical way, and even millimeters or centimeters can be awkward since a foil’s thickness can be much less than a millimeter. The micrometer is defined as one millionth of a meter, and tools like a micrometer screw gauge are designed to measure precisely in this range. For example, 16 micrometers equals 0.016 millimeters, which is a common way to express foil thickness. Using micrometers aligns the unit with the scale of the measurement and common manufacturing tolerances.