English: Ski trails are 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. However, this is just a general "rule of thumb." A trail will be rated by its most difficult part, even if the rest of the trail is easy. In addition, there are many factors which contribute to difficulty rating, such as: width of the trail, sharpest turns, terrain roughness.