Cardiff Half
Cardiff Half Marathon: Complete Training and Race Guide
Everything everyday runners need for one of the UK's biggest half marathons: the flat 13.1 mile route through Cardiff, how to get a place, and a 12-week plan to reach the start line ready.
TL;DR
- The Cardiff Half Marathon is a flat 13.1 mile (21.1 km) race through Cardiff, Wales, and one of the UK's biggest half marathons, held on a Sunday in early October. You enter through the public ballot, a charity place, or one of the organiser's other options.
- The single-loop course is famously flat and fast, passing Cardiff Castle, the Principality Stadium, Penarth, the Cardiff Bay Barrage and Roath Park Lake.
- Run 4 Wales organises the event, and recent editions have hosted a field of around 27,500 runners.
- Give yourself about 12 weeks of structured training, building your long run gradually with a couple of easier weeks and a taper before race day.
- Details change every year, so confirm the current date, fees and entry routes on the official site before you plan around them (as of July 2026).
13.1 miles
21.1 km, the half marathon distance
~27,500
runners in recent editions
2nd biggest
half marathon in the UK
The Cardiff Half Marathon has grown into one of the standout autumn races in the UK running calendar. It combines a genuinely fast course, big crowds and a city-centre atmosphere, which makes it a popular target for a first half marathon as well as a personal best attempt. This guide walks you through what the race involves, how to secure a place, and how to train and pace it sensibly. It assumes you already have a basic running base of a few runs a week.
What is the Cardiff Half Marathon?
The Cardiff Half Marathon is a mass-participation road race over the half marathon distance of 13.1 miles, or 21.1 km, run through the streets of Cardiff, the Welsh capital. It is organised by Run 4 Wales, a charitable trust, and has become the largest mass-participation running event in Wales. It is widely reported as the UK's second-biggest half marathon, behind only the Great North Run, which gives you a sense of the scale and the support you can expect on the course.
The race is typically held on a Sunday in early October, historically the first Sunday of the month. Alongside the main half marathon there are junior and family events on the weekend, and the whole occasion doubles as one of the biggest charity fundraising days in the Welsh calendar. Roads across the city close for the morning, and thousands of spectators line the route, which is a big part of why so many runners come back year after year.
What is the route like?
The course is a single loop and is famous for being flat and fast, which is exactly what you want if you are chasing a time or running your first half. It starts near Cardiff Castle in the city centre, heads out past the Principality Stadium and Cardiff City Stadium, then runs south towards Penarth and the marina. Runners cross the Cardiff Bay Barrage and pass through the heart of Cardiff Bay, taking in the Norwegian Church, the Senedd and the Wales Millennium Centre.
From the bay the route heads north and includes a loop around the scenic Roath Park Lake before returning towards the Civic Centre and Cathays Park for the finish. There are no major climbs, so the main challenge is holding a steady effort rather than surviving hills. Any small rises tend to come early, and the closing miles are flat, which sets you up well for a strong finish if you have paced the first half sensibly.
| Key fact | Detail (as of July 2026) |
|---|---|
| Distance | Half marathon, 13.1 miles (21.1 km) |
| Location | Cardiff, Wales, city-centre start and finish |
| Typical date | A Sunday in early October (autumn). The 2026 race is reported as 4 October; confirm on the official site. |
| Organiser | Run 4 Wales |
| Entry routes | Public ballot, limited paid entry options, and official charity places |
Verified against reputable secondary sources in July 2026. The 2026 date is reported, so confirm the current date, fees and field size on the official site before planning around them.
How do you get a place?
Demand for the Cardiff Half is high, so places do not stay open indefinitely. The main routes in are a public ballot, a limited number of paid general entries when they are released, and official charity places. A general entry gives you a straightforward spot on the start line. A charity place usually comes with a fundraising commitment in exchange for a guaranteed entry, and it is a good option if the ballot is full or you want to support a cause while you run.
Entry mechanics, fees and deadlines change from year to year, and the organiser sometimes adds tour operator, business challenge and international travel packages. The safest approach is to check the official Run 4 Wales race site at cardiffhalfmarathon.co.uk for the current entry options and prices, and to register early once you have decided to commit.
How should you train for it?
For most everyday runners with an existing base, a 12-week block is enough time to prepare well without rushing. The core of any good plan is a gradual build of your weekly long run, a small amount of faster running to sharpen your fitness, and easy runs to carry most of your mileage. The golden rule is to increase distance slowly and to keep the majority of your running comfortable and conversational.
Strength and mobility work is widely recommended to support your running, help you hold form when you tire, and keep your training consistent. Two short sessions a week covering the legs, hips and core sit well alongside a running plan. The outline below is a template to adapt to your own starting point rather than a rigid prescription, and it includes two easier weeks and a taper so you arrive fresh.
| Week | Easy runs | Session | Long run | Focus |
|---|---|---|---|---|
| 1 | 2 x 30-40 min | 6 x 2 min steady | 5 miles | Settle into a routine |
| 2 | 2 x 35-40 min | 8 x 2 min steady | 6 miles | Build easy volume |
| 3 | 2-3 x 40 min | 4 x 4 min tempo | 7 miles | Introduce tempo |
| 4 | 2 x 30 min | 5 x 2 min relaxed | 5 miles | Easier week to absorb work |
| 5 | 3 x 40 min | 5 x 4 min tempo | 8 miles | Rebuild and progress |
| 6 | 3 x 40-45 min | 3 x 8 min tempo | 9 miles | Longer sustained efforts |
| 7 | 3 x 45 min | 6 x 3 min at race pace | 10 miles | Practise goal race pace |
| 8 | 2 x 35 min | 4 x 3 min relaxed | 7 miles | Easier week to recover |
| 9 | 3 x 45 min | 2 x 12 min tempo | 11 miles | Peak endurance |
| 10 | 3 x 45 min | 4 x 6 min at race pace | 11-12 miles | Sharpen at goal pace |
| 11 | 2-3 x 35 min | 3 x 5 min at race pace | 8 miles | Taper begins, cut volume |
| 12 | 2 x 20-30 min easy | 3 x 90 sec strides | Race day, 13.1 miles | Freshen up and race |
How should you pace it?
The flat profile makes even pacing both possible and rewarding. The most common mistake is starting too fast, carried along by the crowd and the downhill early miles. Hold back in the opening two or three miles, settle into a rhythm that feels controlled, and aim to run the second half at the same effort or slightly quicker. That approach, often called a negative split, tends to produce a faster and more comfortable finish than going out hard.
Use your long runs and race-pace sessions in training to learn what your target pace feels like, then trust that feeling on the day. With a big field, the first mile can be congested, so do not panic if it is slightly slow. Take on fluids at the drink stations, and if you are using gels or other fuel, practise with them in training first so nothing is new on race day.
What should you know on race day?
Arrive with plenty of time. City-centre road closures and large crowds mean travel and parking take longer than usual, so plan your journey in advance and aim to reach the start area early. Lay out your kit the night before, pin your number on, and stick to the breakfast and pre-race routine you have tested in training. October mornings in Cardiff can be cool, so an old layer you can discard at the start keeps you warm while you wait.
Line up in the pen that matches your realistic finish time so you are not weaving past slower runners or being swept along too fast. Once you are moving, break the race into sections, enjoy the landmarks and the crowd support, and save something for the flat run back to the Civic Centre finish. Afterwards, keep moving gently, refuel, and give yourself easy days to recover before returning to normal training.
A note on staying healthy
This guide is general training information, not medical advice. Build up gradually, listen to your body, and see a physiotherapist or GP if you have pain, an injury, or any health condition before you start or continue training. Strength and mobility work is widely recommended to support running, but progress it sensibly.
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Frequently asked questions
What is the Cardiff Half Marathon?
It is a flat 13.1 mile (21.1 km) road race through Cardiff, Wales, and one of the UK's biggest half marathons, usually held on a Sunday in early October. It is organised by Run 4 Wales, and you enter through the public ballot, a limited paid entry, or an official charity place.
How many miles is the Cardiff Half Marathon?
It is the standard half marathon distance of 13.1 miles, which is 21.1 km. The course is a single loop through the city and is known for being flat and fast.
When does the Cardiff Half Marathon take place?
It is typically held on a Sunday in early October, historically the first Sunday of the month. The 2026 race is reported to be on 4 October, but dates change yearly, so confirm the current date on the official site.
How do I enter the Cardiff Half Marathon?
The main routes are the public ballot, a limited number of general paid entries, and official charity places that come with a fundraising commitment. Entry options, fees and deadlines change each year, so check the official Run 4 Wales race site and register early.
How long does it take to train for the Cardiff Half?
If you already have a basic running base, about 12 weeks is a sensible block. Build your long run gradually, add a small amount of faster running, include a couple of easier weeks, and taper in the final fortnight so you reach the start line fresh.
Race facts in this guide were verified against reputable secondary sources as of July 2026. Event details including the date, fees, field size and entry routes change each year, so always confirm the latest information on the official Run 4 Wales site at cardiffhalfmarathon.co.uk before you commit.
