Is 3h30 a Realistic Goal for My First Marathon?

Hello there.

My name is Sebastien, I'm 40 years old and I started running 6 months ago. I have never done any sport since I was 12 as I grew up on a boat and later started working as a marine carpenter.

Then the obvious happens, mid-life crisis, you start to worry about your looks, etc...

I'm 1.78 meter and 75 kilos. When I started, I could not run 3km, but I'm very determined and I push myself constantly. I have run 40 times in 6 months and I am now running 3 to 4 times a week.

I have entered the Sevilla marathon in Spain which will be held four months from now. My PB on a 10k is 47 min and on a half marathon is 1 h 45.

My question is: is 3h30 a realistic target for Sevilla?

Many thanks.

– Sebastien

Answer by Dom: Hi Sebastien, thanks for your question about your marathon time goal. Based on your current times, 3h30 isn't yet attainable – here's why, and here's the road to get there.

1. Why 3h30 isn't attainable yet, based on the numbers
2. Why the prediction itself is shakier for a six-month runner
3. Why your first marathon is different from your 10k and half PBs
4. How to build toward 3h30 over the next 18 months

Why a 3h30 Marathon Isn't Yet Attainable

I plugged your times into the Race Conversion Calculator on this website.

At the moment your 10k time of 47 minutes indicates an ability to run a marathon in 3:36. And your 1:45 half marathon indicates an ability to run a marathon in 3:38.

That's not far off, but it is not there.

For a 3:30 marathon, you'd like your 10k to be at about or lower than 45 minutes and your half marathon at or lower than 1:40.

So, more work to do. But even if your 10k and half marathon were that fast, your first marathon is different.

Why the Prediction Itself Is Shakier for You Right Now

Calculators like this one work off a simple idea: race times scale in a predictable way across distances, for a given level of durable, race-tested endurance. For a runner with years of consistent mileage and a few marathons banked, that scaling holds tight – accuracy is typically within 5-10%.

You don't have that yet. Six months of running. Forty runs total. A year ago you hadn't run at all. Your 10k and half times reflect real fitness, no question – you've built that fast, and it's impressive. But they reflect general fitness and effort tolerance, not the specific muscular endurance needed to hold marathon pace for 26.2 miles.

That's why the calculator hands you a hopeful number – 3:36 to 3:38 – while the real result is likely to overshoot it if you don't have the long-run miles banked first. Aiming more modest for your first marathon isn't just caution on my part. The maths behind the prediction says the same thing.

Why Your First Marathon Is Different

You have just started running. I normally push back when people start their running and immediately want to jump to a marathon. The reality of the marathon is... it is a bloody long way. You need a certain amount of hardness in your legs that is built up over months and months of training.

That's why for many people the first marathon turns out to be a bit of a disaster. They come to a site like this, plug in the numbers and aim for a 3:38 marathon. And then discover that during the last 10k everything falls apart and they finish in 4+ hrs.

Holding it together in the last 10k is the hardest part in the marathon.

That's why I'd strongly urge you to aim for a more modest goal. Aim for sub-4 hrs, maybe. Or simply aim to complete it. And be proud of yourself when you do so – it is a big accomplishment.

How to Achieve a 3h30 Marathon

You can still aim for a 3:30 marathon. You just need more time. Keep your consistency up over the next 18 months. Keep that long run going. Running life is great when every weekend you tick off a half marathon in your long run. You then have a fantastic base to start your marathon training.

When that is your starting point for, say, a 16-18 week marathon training program, you then have a good opportunity to:

• hit 20 miles multiple times in your cycle
• add some quality miles to your long runs (progression runs or fast-finish runs)
• do a mid-week long run of at least 90 minutes to support your cardiovascular base building
• keep some quality workouts in your running schedule, starting with intervals, moving to tempos and goal pace workouts as time progresses

And that will set you up well to shoot for a more aggressive time goal. Still, the marathon is a beast and it can take multiple attempts and a number of years of training to really ace the marathon.

Check out the Marathon Training Tips page and supporting pages in the marathon section to learn more about marathon training.

Hope this helps. Best of luck with your marathon plans and with the mid-life crisis. Stay hungry, stay foolish...

Kind regards,
Dom

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