Why grading exists
Trail grading exists for one reason: to stop riders dropping into something they can't ride out of. It's not a measure of how fun a trail is, how fit you need to be, or how long it takes. It's a measure of the technical features (gaps, drops, rock, exposure) and what skill is required to ride the hardest move on the trail.
That means a green can be a 25 km climb to a viewpoint — easy moves, hard fitness. And a black can be a 400 m descent with one no-fail drop near the bottom.
UK trail-centre grading
Used at Coed-y-Brenin, BikePark Wales, Glentress, Whistler-equivalent trail centres across the UK and most of Ireland's purpose-built loops (Ballyhoura, Ticknock, Davagh, Slieve Bloom). Five grades:
| Grade | Symbol | What to expect |
|---|---|---|
| Green | ● green | Wide doubletrack, gentle gradient, no technical features. Family / first-timer ground. |
| Blue | ● blue | Singletrack, smooth surface, some small rolls and berms. No drops, no jumps with gaps. |
| Red | ● red | Sustained singletrack with rock, roots, small drops, optional jumps, jumps with safe rollovers. The "standard" trail-centre red is what most weekend riders can handle on a trail bike. |
| Black | ● black | Steep, technical, often with mandatory features (drops you can't roll, jumps with gaps). Knee pads recommended. |
| Orange / Pro / Double-black | ● orange | UK trail centres add an extra grade for bike-park gravity tracks — large gaps, mandatory drops, exposure. Full-face territory at most parks. |
IMBA (US) grading
The International Mountain Bicycling Association uses a five-grade ski-style scale that is broadly compatible with the UK system but reads slightly easier in the middle and harder at the top.
| Grade | Symbol | What to expect |
|---|---|---|
| Easiest | White circle | Smooth, flat, <3% gradient. Beginner-friendly. |
| Easy | Green circle | Wide tread, low-grade obstacles <5 cm, gradient <10%. |
| More difficult | Blue square | Singletrack, obstacles up to 20 cm, gradient up to 15%, some unavoidable features. |
| Very difficult | Black diamond | Obstacles up to 38 cm, gradient up to 20%, drops up to 60 cm. |
| Extremely difficult | Double black | Anything above. Unavoidable large drops, exposure, mandatory technique. |
European single-track scale
The Single Trail Skala (STS) — a six-grade S0–S5 system originating in Germany — is what you'll see on hiking-MTB shared trails across the Alps and on platforms like Trailforks. It's measured purely on the trail surface, not the gradient or scenery.
| Grade | Surface | Skill |
|---|---|---|
| S0 | Hardpack, no obstacles | Anyone |
| S1 | Small roots / stones, gradient to ~15° | Basic technique |
| S2 | Bigger roots / loose stones, stairs, switchbacks | Confident weight shift, basic braking control |
| S3 | Slabby rock, drops >30 cm, gradient >30° | Advanced bike handling |
| S4 | Steep, loose, mandatory drops >70 cm, tight switchbacks | Expert. Hike-a-bike often the option. |
| S5 | Vertical chutes, big drops, exposure | Pro / extreme |
How the systems map across
Roughly — and this is rough, not gospel:
- UK green ≈ IMBA green ≈ STS S0
- UK blue ≈ IMBA blue ≈ STS S1
- UK red ≈ IMBA blue/black ≈ STS S2 (sometimes S3 in places)
- UK black ≈ IMBA black ≈ STS S3
- UK orange / pro line ≈ IMBA double-black ≈ STS S4+
How to use grading sanely
- Drop down one grade in a new venue. Local grading is graded by the locals. What's a red at one trail centre will feel like a black at another.
- Walk anything you're not sure of. Especially mandatory features near the bottom of a trail when you're already tired.
- Bike park is always graded harder. A bike-park blue can have jumps a trail-centre blue would never have. Read the trail-board notes.
- Wet doesn't change the grade — it changes the consequences. A rooty red in Ireland after a week of rain rides like a black. Slow down.