Perimeter facts for kids
In geometry, perimeter is the distance around a flat object. For example, all four sides of a square rhombus have the same length, so a rhombus with side length 2 inches would have a perimeter of 8 inches (2+2+2+2=8).
Reallife objects have perimeters as well. A football field, including the end zones, is 360 feet long and 160 feet wide. So the perimeter of the field is 360+160+360+160=1040 feet.
The perimeter of a circle is usually called the circumference. It may be calculated by multiplying the diameter times "Pi". Pi is a constant which is equal to 3.14159; however, the places to the right of the decimal are endless. The number of places used depend on the accuracy required for the result.
Images for kids

The NeufBrisach fortification perimeter is complicated. The shortest path around it is along its convex hull.