The metric SI unit used for measuring length is the meter (m).
In the International System of Units (SI), the meter serves as the foundational unit for length. It was defined in 1983 as the distance that light travels in a vacuum in 1/299,792,458 seconds. The meter is widely used around the world and is a crucial part of various scientific and engineering calculations.
To give you a sense of scale, one meter is slightly over three feet, which makes it a convenient unit for many everyday measurements, such as measuring the height of a person or the length of a room. In practical applications, lengths can also be expressed in kilometers (1,000 meters) for larger distances or millimeters (1/1,000 of a meter) for smaller measurements.