Marathon Eryri (Snowdonia Marathon): Course, Elevation & Route Profile
Marathon Eryri circles Yr Wyddfa (Snowdon), the highest mountain in Wales and England. It starts at 10:30 on 24 October just outside Llanberis and finishes on Llanberis High Street – and between the two lie forty-two kilometres of mountain road, 797 metres of climbing and three passes. Founded in 1982 as a deliberate answer to the city marathons then springing up, it is allocated by ballot and has been one of Britain's hardest road marathons for four decades.
Course & Elevation
The course is three climbs and three descents, and it opens with the biggest one.
From 124 metres just outside Llanberis it rolls gently downhill for two kilometres, then at kilometre 3 the Llanberis Pass ramp begins: eleven kilometres of road rising from 120 to 340 metres, steepest between kilometre 6 and 7. At the top sits Pen y Pass, the high point of the first half, framed by the walls of the Snowdon massif.
Then comes the longest descent of the day. From kilometre 8 the course falls almost without interruption to kilometre 21 – from 340 metres to 45. On the way it turns off at the Pen-y-Gwryd junction (km 9.5) onto the old road and runs about two kilometres downhill on gravel to the campsite, with a short sharp pull back up to the main road. From kilometre 14 it flattens: the stretch through Nant Gwynant along Llyn Dinas is the only genuinely flat running in the race, and the day's lowest point is in the Beddgelert basin.
The second climb is the underrated one. From kilometre 22 to 25 the A4085 climbs from 89 to 195 metres up towards Rhyd-Ddu, and from there to kilometre 34 the course stays in a rolling band between 125 and 160 metres – not a climb you can settle into, but twelve kilometres that never level out.
The third climb decides everything. At kilometre 34, just past Waunfawr, the course stands at 127 metres; six kilometres later, at kilometre 39.4, at 372.5 metres – the highest point of the race. That is almost 250 metres of climbing after thirty-four kilometres of marathon, part of it on unmetalled ground, and the six-hour cut-off at Ysgol Waunfawr (mile 22, km 35.4) sits at its foot. From the top the road drops 260 metres in two and a half kilometres into Llanberis and the finish.
Pacing Strategy
There is exactly one rule for this marathon: the race starts at kilometre 34.
Everything before that is preparation. The Llanberis Pass in the first third feels manageable on fresh legs, and that is precisely what makes it dangerous – push the eleven kilometres from kilometre 3 to 8 at race effort and the substance the final climb needs has already been spent. Even effort here means a minute to ninety seconds per kilometre slower than your flat pace, with no glance at the watch.
The long descent from kilometre 8 to 21 is the second trap, and it costs more than the climb. Thirteen kilometres downhill, two of them on gravel, shedding nearly three hundred metres – that takes more out of eccentrically loaded quads than it gives back in time. Let it run here and you arrive at kilometre 34, at the foot of the decisive climb, on dead legs.
The rolling middle from kilometre 22 to 34 is the section without a story: no big climb, no real descent, few spectators, plenty of wind across open ground. You do not lose dramatically here, you lose slowly.
And then the final climb: 245 metres of ascent from kilometre 34 to 39.4, its categorised core 3.5 kilometres at 6.9 per cent. Realistically most runners walk part of it – and that is not a defeat, it is the faster answer for many. Anyone still running gains double-digit places on that ramp. Reach the top and the last two and a half kilometres are a gift: 260 metres of descent down to the High Street, but steep enough that tired quads pay for it.
Training plan for Marathon Eryri (Snowdonia Marathon): 12-week build
For a competitive age-group runner Marathon Eryri takes roughly 3:15 to 5:00 – considerably longer than a flat marathon off the same fitness. There is no overall time limit, but a six-hour cut-off closes at 16:30 at Ysgol Waunfawr at mile 22 (km 35.4), which is exactly the foot of the final climb.
Three qualities decide it. First, sustained uphill strength endurance: the Llanberis Pass takes fifty to seventy minutes and the final climb forty to sixty, so the training is twenty- to forty-minute continuous uphill blocks, not hill sprints. Second – and this is almost always underestimated – eccentric durability: the course sheds nearly three hundred metres between kilometre 8 and 21, then another 260 in the last two and a half kilometres. Downhill running has to be trained, or the quads go in the final third. Third, the ability to climb late: putting hill repetitions at the end of a long run is the single most specific session for this race.
Then there is the surface. Two kilometres of gravel descent and a short unmetalled stretch on the final climb are enough to make pure road shoes unpleasant – a shoe with some tread, and a few training runs on gravel, pay for themselves.
Fuelling is well covered: twelve stations, water at all of them, Mountain Fuel electrolyte and energy drink at miles 6.5, 11, 13, 15, 16.5, 18, 20 and 22, and gels at miles 6.5, 18 and 22. Because the race lasts longer than a flat marathon, carbohydrate per hour matters more than carbohydrate per kilometre – practise it that way.
And finally the weather. Late October at 370 metres in Eryri can mean rain, wind and single-digit temperatures; the organiser advises explicitly to carry some form of body cover. A light windproof layer worn in the race should have been tested in training – as should gloves, which are wanted at the first pass and worn by nobody at the finish.
Course Map
Profile Parameters
Slope Distribution
Climbs on Route
| Start (km) | Length | Ø Gradient | Max Gradient | Elev Gain | Category |
|---|---|---|---|---|---|
| KM 3.5 | 3.9 km | 6.3% | 12.7% | +246m | Cat. 3 |
| KM 21.0 | 3.3 km | 4.5% | 7.4% | +150m | Cat. 4 |
| KM 34.9 | 3.5 km | 6.9% | 11.5% | +242m | Cat. 3 |
Climb categories follow the road-cycling convention and rate the terrain itself (length and gradient) regardless of sport: Cat. 4 marks the easiest rated climbs, Cat. 1 the hardest, and HC (hors catégorie, “beyond categorization”) is reserved for the most brutal ascents. Short climbs below the Cat. 4 threshold stay unrated.
Course as GPX
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Adaptive race preparation
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Ben connects your goal, the course, current load, recovery, and calendar. Your plan stays pointed at race day even when real life is not perfectly plannable.
Frequently asked questions
How long is Marathon Eryri (Snowdonia Marathon)?
Marathon Eryri (Snowdonia Marathon) is 42.2 km long. That distance shapes how much aerobic endurance, pace durability, and race-specific work belong in the training plan.
How much elevation gain does Marathon Eryri (Snowdonia Marathon) have?
Marathon Eryri (Snowdonia Marathon) has around 797 m of elevation gain over 42.2 km. That affects pacing, muscular load, and preparation for late-race sections.
What is the route profile of Marathon Eryri (Snowdonia Marathon)?
Marathon Eryri (Snowdonia Marathon) is classified as Hilly, averaging 18.9 vertical metres per kilometre. 24% of the route is flat, 34% climbs moderately (2 to 6%) and 5% is steeper than 6%.
What climbs does Marathon Eryri (Snowdonia Marathon) have?
The hardest climb of Marathon Eryri (Snowdonia Marathon) starts at kilometre 3.5, runs for 3.9 km at an average of 6.3% and gains 246 metres. Cycling-convention rating: Cat. 3. 3 climbs are mapped in total.
Is Marathon Eryri (Snowdonia Marathon) a loop course?
Yes, Marathon Eryri (Snowdonia Marathon) is laid out as a loop: start and finish are in the same place.
Is there a GPX file for the Marathon Eryri (Snowdonia Marathon) course?
Yes. The Marathon Eryri (Snowdonia Marathon) course is on this page as a free GPX download — ready to import into Garmin, Wahoo, Komoot, Strava or any other app that reads GPX.
How should I prepare for Marathon Eryri (Snowdonia Marathon)?
Preparation for Marathon Eryri (Snowdonia Marathon) should account for 42.2 km, 797 m of elevation gain, current training load, and available training time. An adaptive plan helps place key sessions without ignoring recovery and real life.
What pacing strategy works for Marathon Eryri (Snowdonia Marathon)?
The pacing strategy for Marathon Eryri (Snowdonia Marathon) should reflect 42.2 km, 797 m of elevation gain, and your current fitness. Start controlled and keep margin for sections where the profile or fatigue makes target pace harder.
When does Marathon Eryri take place?
Marathon Eryri takes place on October 24, 2026.
Where does Marathon Eryri take place?
Marathon Eryri takes place in Llanberis, United Kingdom.
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