1 span is exactly 9 inches. In SI units 1 span is 0.2286 meters. A span is the same size as a quarter (1/4 yard).
1 Step:
The distance covered by a single step assuming a stride length of 0.762 meters or 2.5 feet. Although stride length will vary by person and activity this may be useful in estimating distance traveled from the reading on a pedometer.