Identify the shape, line segment, or object whose length you need
Determine the starting point and ending point
Use a ruler, tape measure, or measuring tool to measure between the two points
Read the measurement at the endpoint
If using coordinates, apply the distance formula
If using a scale or map, use the given scale to convert to actual length
If the object is curved, use a flexible measuring tool or string, then measure the string
Check the unit of measurement and convert if needed