Cwm Nantcol via Y Llethr and Crib-y-rhiw up Diffwys: route map, distance and time
750 m · Snowdonia
A hard mountain walk to the summit from Cil-cychwyn public path.
Cwm Nantcol via Y Llethr and Crib-y-rhiw starts at about 175 m and gains 700 m over 7.6 km to 728 m on the track. The first kilometre climbs 80 m. The steepest kilometre is the one ending at 2 km, which climbs 151 m at an average of 15%. It keeps climbing at 12% to the top.
Cwm Nantcol via Y Llethr and Crib-y-rhiw at a glance
| Distance | 7.6 km one way, to the top |
|---|---|
| Ascent | 730 m |
| Climb on the track | 700 m up, 147 m down on the way |
| Start and top of the track | 176 m to 741 m (summit 750 m) |
| Steepest 500 m | About 18%, from 4.3 km |
| Steeper than 1 in 5 | 5% of the way |
| Time up | 2h 45m by Naismith's rule |
| There and back | 4h 15m, down the same way |
| Grade | Hard |
| Start | Cil-cychwyn public path |
| Start grid reference | SH 634 260 |
| Summit grid reference | SH 661 234 |
| Parking | No checked car park for this start; find lawful parking nearby |
Cwm Nantcol via Y Llethr and Crib-y-rhiw map
The track from the start (green) to the summit (blue), with a marker at each kilometre.
Height profile and getting to the start
Download the Cwm Nantcol via Y Llethr and Crib-y-rhiw GPX
Ascent only: plan your way down. A planning track, not checked on the ground; it doesn't show safe scrambling moves. Track data © OpenStreetMap contributors (ODbL), heights from a terrain model.
Cwm Nantcol via Y Llethr and Crib-y-rhiw kilometre by kilometre
Height, climb and average gradient for each kilometre of the track, with a grid reference at the end of each one to check your position on the map.
| At | Height | Climb | Gradient | Grid ref |
|---|---|---|---|---|
| 1 km | 255 m | +80 m | 8% | SH 636 256 |
| 2 km | 406 m | +151 m | 15% | SH 640 250 |
| 3 km | 518 m | +113 m | 11% | SH 645 252 |
| 4 km | 636 m | +117 m | 12% | SH 655 253 |
| 5 km | 697 m | +61 m | 6% | SH 660 255 |
| 6 km | 643 m | -54 m | -5% | SH 664 247 |
| 7 km | 658 m | +15 m | 2% | SH 664 238 |
| 7.6 km | 728 m | +69 m | 12% | SH 661 234 |
How long Cwm Nantcol via Y Llethr and Crib-y-rhiw takes
| Pace | To the top | There and back |
|---|---|---|
| Brisk 6 km/h, 8 min per 100 m up | 2h 15m | 3h 30m |
| Steady (Naismith) 5 km/h, 10 min per 100 m up | 2h 45m | 4h 15m |
| Relaxed 4 km/h, 12 min per 100 m up | 3h 20m | 5h 15m |
Times leave out stops. Coming down the same way, the table counts the ascent once; steep descents on rough ground can be as slow as the climb.
- Today: sunrise 07:49, sunset 18:12. Start by 12:57 to be down before dark, allowing 4h 15m for the walk and an hour for stops.
- Tomorrow: sunrise 07:51, sunset 18:10. Start by 12:55 to be down before dark, allowing 4h 15m for the walk and an hour for stops.
Diffwys summit weather for this route
-
Poor Today Monday 19 October
Moderate drizzle, up to 7°C at the summit, feeling as cold as -2°C, summit wind 40 mph gusting 49 mph, 98% chance of rain. Rated Poor. Sunrise 07:49, sunset 18:12.
-
Marginal Tomorrow Tuesday 20 October
Moderate drizzle, up to 6°C at the summit, feeling as cold as 0°C, summit wind 24 mph gusting 30 mph, 64% chance of rain. Rated Marginal. Sunrise 07:51, sunset 18:10.
Best day of the next seven for Cwm Nantcol via Y Llethr and Crib-y-rhiw: Tuesday 20 October, with summit gusts around 30 mph and a 64% chance of rain.
Before you go, also check: MWIS Snowdonia forecast · Met Office mountain forecast.
What to take today
- An insulated jacket, hat and warm gloves: it feels like -2°C on top.
- Waterproof jacket and overtrousers: 98% chance of rain.
- A windproof layer, and poles for balance in gusts to 49 mph.
- Map and compass, and the skills to use them. A phone is a backup, not a plan.
- A head torch, food, water, a charged phone and a small first aid kit.
About Diffwys
More about Diffwys, with the live forecast.
Challenges that include Diffwys
More walks from Cil-cychwyn public path
Routes in Peakify's guides that start within 500 m of this one, for another day from the same car park.
- Cwm Nantcol western approach up Y Llethr
Other routes up Diffwys
| Route | Distance | Ascent | Time up | Grade |
|---|---|---|---|---|
| Cwm Mynach eastern approach | 4.2 km one way | 570 m | 1h 45m | Hard |
| Tal-y-bont via Diffwys West Top | 6.5 km one way | 490 m | 2h 5m | Hard |
In an emergency
Call 999, ask for the police and then mountain rescue. Give your location (the start is at SH 634 260, the summit at SH 661 234), what happened and how many are in your group. If you have no signal for a call, a text to 999 works once you have registered your phone with emergencySMS: text "register" to 999 before you go.
Cwm Nantcol via Y Llethr and Crib-y-rhiw: questions and answers
How far is Cwm Nantcol via Y Llethr and Crib-y-rhiw?
Cwm Nantcol via Y Llethr and Crib-y-rhiw is 7.6 km one way to the summit of Diffwys, with 730 m of ascent. There and back by the same way is about 15.2 km.
How long does Cwm Nantcol via Y Llethr and Crib-y-rhiw take?
About 2h 45m to the summit of Diffwys and 4h 15m there and back by Naismith's rule (5 km/h plus 10 minutes per 100 m of ascent), before stops. A relaxed group takes nearer 5h 15m for the round trip.
How steep is Cwm Nantcol via Y Llethr and Crib-y-rhiw?
The steepest 500 m averages about 18%, starting 4.3 km from the start, and 5% of the way is steeper than 1 in 5. Cwm Nantcol via Y Llethr and Crib-y-rhiw climbs 700 m in all on the track.
Where do you park for Cwm Nantcol via Y Llethr and Crib-y-rhiw?
Cwm Nantcol via Y Llethr and Crib-y-rhiw starts from Cil-cychwyn public path. The grid reference is SH 634 260. No checked car park for this start; find lawful parking nearby
Is Cwm Nantcol via Y Llethr and Crib-y-rhiw suitable for beginners?
Not as a first mountain. Peakify grades it Hard: steep, rough ground where a slip matters. Build up on an easier route first.
What time should I start Cwm Nantcol via Y Llethr and Crib-y-rhiw today?
By 12:57 at the latest. Sunset on Diffwys today is 18:12, Cwm Nantcol via Y Llethr and Crib-y-rhiw takes about 4h 15m there and back, and that leaves an hour for stops. Start earlier in winter or if the forecast turns.
Is there a GPX for Cwm Nantcol via Y Llethr and Crib-y-rhiw?
Yes. Download it from this page. It is an ascent-only planning track from the start to the summit, plotted on OpenStreetMap paths and not checked on the ground.