Usually a tape measure will do.
A tape measure is commonly used to measure the circumference of the head.
Walter's head measures around 24 inches in circumference.
The circumference is about 28.9
Because it is difficult to wrap a metre ruler around someone's head.
The circumference of a circle measures the distance around the circle.
A measuring tape is flexible - a metre rule isn't !
If a circle measures 83 inches in circumference the diameter is: about 26.42 inches. You can easily do this calculation for other circles by dividing the circumference by Pi (about 3.1416).
This instrument is a balance.
A circumference of 6.28 inches measures exactly 6.28 inches!
Head circumference of 3 year old?
The square footage of a circle that measures 159 feet in circumference is about 2,012 square feet.
An instrument that measures heat and cold is called a thermometer.