
Gwynedd, United Kingdom · Saturday 17 October 2026
Take on a true test of endurance in the rugged terrain of Wales with the Cadair X Half Marathon. This challenging trail race ascends and descends the slopes of Cadair Idris, a majestic mountain in Snowdonia National Park. This race offers a chance to conquer a formidable peak. The views from the summit are a reward for those who dare to tackle this demanding course.
Adjusted Time
3:03:21
Time difference: +78.3 minutes compared to a flat, road, temperate course.
On our difficulty model, Cadair X Half Marathon plays about 69 minutes slower than an average road half marathon for a 1:30 runner. It ranks #4 hardest of 450 half marathons we analyse, and #1 of 89 in United Kingdom. Use the calculator above to see the exact adjusted time for your own goal pace.
Estimated finish times on this course versus the same effort on an average road half marathon, based on its elevation, surface, and expected race-day temperature.
| Average-course time | On Cadair X Half Marathon | Difference |
|---|---|---|
| 1:30:00 | 2:37:23 | +1:07:23 |
| 1:45:00 | 3:03:21 | +1:18:21 |
| 2:00:00 | 3:29:49 | +1:29:49 |
| 2:15:00 | 3:56:48 | +1:41:48 |
| 2:30:00 | 4:24:17 | +1:54:17 |
| 2:45:00 | 4:52:15 | +2:07:15 |
| 3:00:00 | 5:20:42 | +2:20:42 |
Use the calculator above for your exact goal time. Want a prediction from your own training? Try the marathon time predictor.
Cadair X Half Marathon is a half marathon held in Gwynedd, United Kingdom. It is scheduled for Saturday 17 October 2026. The course is run on trail surface with 1107m of total climbing, with its high point near 886m above sea level. For registration and full race details, visit the official Cadair X Half Marathon website.
This is a very challenging course with 1107m of total climbing - well above the average trail marathon - topping out around 886m above sea level. Hill training is essential, and you should expect a slower finish time than on a flat course.
Based on historical weather data for October, the expected race day conditions are as follows. Near-ideal running temperatures are expected, ranging from 6°C to 17°C. This temperature range is widely considered optimal for marathon performance, allowing efficient heat dissipation without cold-related issues. There is a low chance of rain (0%), so dry conditions are likely.
Cadair X Half Marathon is a trail race, meaning the course includes unpaved surfaces such as dirt, gravel, or forest paths. Trail surfaces are usually slower than the road equivalent - often by 10-20% - because of uneven footing, technical sections, and frequently steeper gradients, though a smooth, non-technical or downhill trail can run faster than that suggests. Trail-specific shoes with good grip are recommended.
Looking for an easier marathon or a tougher challenge? You can also compare Cadair X Half Marathon against other half marathons to find the right race for your goals.
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