Mountain biking trail grades
Mountain biking is a potentially hazardous activity carrying a significant risk. It should only be undertaken with a full understanding of all inherent risks. These trail grades are guidelines that must always be used in conjunction with the exercise of your own experience, intuition and careful judgment.
Grade Trail and surface types   Gradients and technical trail features Skills needed
G.1 Easy Relatively flat, wide and firm surfaces. Trail surface might be loose, uneven or muddy at times, Might include short flowing single track-style sections. Climbs and descents are mostly shallow. No challenging features.   Basic bike skills are required for this grade. It is suitable for beginners or novice cyclists or for most people in good health
G2 Intermediate As for ''easy", plus specially constructed single track trails.   Trail surface might include small obstacles of root and rock. Most gradients are moderate but might include short steep sections.   Includes small technical trail features (such as roots and rock). Basic off-road riding skills to cope with uneven surfaces and small obstacles. Suitable for intermediate cyclists or mountain bikers with basic off-road riding skills. A good standard of fitness can help.
G3 Difficult Steeper and tougher, mostly single track with technical sections.   Expect very variable surface types. A wide range of climbs and descents of a challenging nature will be present. Expect boardwalks, large rocks, medium steps, drop-offs, cambers and water crossings. Good off-road skills and techniques to cope with technical trail features. Suitable for proficient mountain bikers with good off-road skills. A higher level of fitness and stamina is required.
G4 Severe As for " difficult", but with an expectation of greater challenge and continuous difficulty. Can include any useable trail and might include exposed open hill sections. Expect large, committing and unavoidable technical trail features.   Sections will be challenging and variable. Might also have 'downhill' style sections.   Advanced level off-road skills and technical ability. Suitable for expert mountain bike users, used to physically demanding routes. Suitable for very active people used to prolonged effort.
G5 Extreme: Severe constructed trails and/or natural features. All sections will be challenging. Includes extreme levels of exposure or risk. Jumping ability obligatory. Will include a range of small, medium and large technical trail features, including downhill trails, free ride sections and mandatory jumps.   A good standard of fitness is recommended but technical skills are more important.