Your first marathon: a realistic goal time

Why a first marathon time is hard to predict

The marathon is 42.2 km (26.2 miles). That's a long way past the 5 km (3.1 miles) or 10 km (6.2 miles) most people can run comfortably when they sign up, so the honest starting point is this: your first marathon is a new distance, not just a longer version of something you've already raced.

Race time predictors — calculators that turn a 10 km or half marathon time into a predicted marathon time — assume you've already done months of marathon training. They aren't wrong, they're answering a different question. Used on a first-timer halfway through a training block, they tend to produce a number that's too quick.

NHS guidance suggests adults aim for at least 150 minutes of moderate activity a week. That's a good floor for health, but it's not a marathon plan, and it won't tell you what you'll run on the day.

The three things that decide your time

Before you pick a number, look at what your training actually says.

• Weekly distance: the total kilometres you run in a week, easy runs included. It's the biggest single influence on how the last 10 km (6.2 miles) will feel.
• Your long run: the longest run of your week, at an easy to steady effort. Time on feet is the goal — it teaches your body to keep going for hours.
• Consistency: how many weeks in a row you've run, rather than how fast any single run was. Three steady months beat one heroic fortnight.

Then there's race day itself. Going out too fast, skipping drinks, a hilly course or a warm morning can all move your finish by more than a small change in fitness would. Not sure your block is long enough? How long to train for a marathon walks through the trade-offs.

A plain-English way to set a goal

Here's a rule of thumb many coaches use. Take a half marathon (21.1 km / 13.1 miles) you've run during this training block, double the time, and add 10 to 20 minutes. It's rough — it assumes the half went well and your mileage is steady — but it's a sensible place to start.

If you haven't raced a half, work in buckets instead:

• Training went well — steady weeks, long runs up to about 32 km (20 miles), feeling good: pick a finish time and a stretch time 10–15 minutes quicker.
• Training was okay — a few missed weeks, long runs a little shorter: pick a finish time and leave it there.
• Training was patchy — illness, injury, a busy job: make finishing comfortably the goal. That is still a marathon.

A goal you beat feels better than a goal you chase.

Goals that survive race day

Runners often set three versions of the same goal. Your A goal is the day everything goes right: good sleep, a cool morning, no stomach trouble. Your B goal is the realistic one you'd be pleased with. Your C goal is finishing, ideally still smiling.

The C goal isn't a consolation prize. On a first marathon it's the one that gets you to the start line without dread, and the one still standing if the day turns warm or your legs have other ideas.

The last couple of weeks matter too — the taper is when the training you've banked gets to show up.

How to pace it

Pace just means minutes per kilometre at a steady effort. Whatever number you settle on, run the first 5 km (3.1 miles) slower than it. It should feel almost too easy — you're banking patience, not time.

Aim for even effort rather than perfectly even pace. Hills take more out of you, so ease on the climbs and let the descents come. Walking through a drinks station costs seconds and can save minutes later. Start your fuelling early: the carb loading guide covers the last 48 hours, and your easy runs should stay genuinely easy all block.