What is the difference between length and distance?

Distance is a numerical description of how far apart objects are.

In physics, distance may refer to a physical length or estimation based on other criteria.

In mathematics, a distance function or metric is a generalization of the concept of physical distance.

Length most commonly refers to the longest dimension of an object.

Length may be distinguished from height, which is vertical extent, and width or breath, which is the distance from side to side, measuring across the object at the right angles to the length.

Units:

In physical sciences and engineering, the word “length” is synonymous with “distance”.

There are several units that are used to measure length. Units of length may be based on length of human body parts, the distance travelled in a number of paces, the distance between landmarks or places on the Earth or arbitrarily on the length of some fixed object.

In the international system of units (SI), the basic unit of length is meter

Some of the unit conversions are,

1 kilometer = 1000 meter
1 meter = 100 centimeter
1 meter = 1000 millimeter
1 centimeter = 0.01 meter
1 decimeter = 0.1 meter

For more info on basic unit conversions, visit Converter