Convert millimeters to centimeters (mm to cm)

One millimeter is exactly 0.1 centimeters. That is the meaning of the metric prefixes, not a measurement: milli is a thousandth, centi a hundredth and kilo a thousand, so every conversion inside the metric system is a power of ten and nothing has to be looked up.

Worked through: 25 mm x 0.1 = 2.5 cm.

Going the other way, one centimeter is 10 millimeters.

To convert without a calculator, multiply by 0.1. Rounding that to 0.1 is within 0% for most purposes.

A decimal shift in the easier direction. Both are metric, so there is no factor to remember; divide by ten and move on. The reason it gets searched at all is that technical drawings use millimeters while everyday description uses centimeters.

Precision is worth matching to the input. A measurement given as 1 mm carries one or two significant figures, and reporting its conversion to six implies a precision the original never had.