Good question, because most people don’t have any use for one. A diameter tape measure is a measuring tape whose scale is stretched out by a factor of pi. This allows you to wrap it around a round object, such as a pipeline or tree trunk, and read its diameter directly on the scale. You don’t need to divide by 3.14159.
Here are some other names that people call these tapes:
- pi tapes
- circumference tapes (a misnomer)
- pipe tapes
- Lufkin pi tapes
- OD tapes
- outside diameter tapes
- pi-Cobra tapes
- pie tapes