For marketing purposes, rice is classified as short, medium or long grained. Shown here are examples of each type.

Grain length class actually reflects the grain length to width ratio as defined by the USDA Federal Grain Inspection Service Grain Inspection Handbook.

The actual length to width ratio is determined by laying 15 grains side by side and measuring them, then lining up the same 15 grains end to end and measuring them.  The ratio of length to width determines the grain class.

Rough or Paddy Rice (before milling, hulls intact)
Long        3.4 to 1 and more
Medium   2.3 to 3.3 to 1
Short        2.2 to 1 and less

Brown Rice (hulls have been removed but bran intact)
Long        3.1 to 1 and more
Medium   2.1 to 3.0 to 1
Short        2.0 to 1 and less

Milled Rice (hulls and bran layers have been removed)
Long        3.0 to 1 and more
Medium   2.0 to 2.9 to 1
Short        1.9 to 1 and less