Begin by establishing a reference point at the start of the measurement, such as the edge of the surface. Lay the bill flat across the distance you’re trying to measure.
If the distance is longer than a single bill, mark the endpoint with a pencil (or your finger) and lay the bill out again, continuing until the measurement is complete.
Multiply the length you measured in bills by 6.14, and you'll have the measurement in inches. For instance, a length of two and a half dollar bills would be a bit over 15 inches.