quality:correction
Ski trail ratings

In most ski resorts, the runs are graded according to comparative difficulty so that skiers can select appropriate routes. The grading schemes around the world are related, although with significant regional variations. A beginner-rated trail at a large mountain may be more of an intermediate-rated trail on a smaller mountain.

In the United States and Canada, there are four rating symbols: Easy (green circle), Intermediate (blue square), and Difficult (black diamond), and Experts Only (double black diamond) Ski trail difficulty is measured by percent slope, not degree angle. A 100% slope is a 45-degree angle. In general, beginner slopes (green circle) are between 6% and 25%. Intermediate slopes (blue square) are between 25% and 40%. Difficult slopes (black diamond) are 40% and up. Although slope gradient is the primary consideration in assigning a trail difficulty rating, other factors come into play. A trail will be rated by its most difficult part, even if the rest of the trail is easy. Ski resorts assign ratings to their own trails, rating a trail compared only with other trails at that resort. Also considered are width of the trail, sharpest turns, terrain roughness, and whether the resort regularly grooms the trail.