How to Run a 3:45 Marathon: The Ultimate Guide to Breaking 3 Hours 45 Minutes

Starting your running journey should feel exciting, not overwhelming. Our training plans give you the structure, support, and flexibility you need to go from your first step to running a marathon, no matter your starting point.

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Running a marathon in 3 hours 45 minutes is a big achievement for many runners, and with good reason. Hitting that time shows you’ve built solid endurance, the ability to hold pace for the long haul, and the discipline to train consistently over weeks and months. For a lot of runners, it’s the kind of milestone that proves you’re no longer just getting round the distance – you’re racing it with purpose and testing what you’re really capable of.

But let’s be clear: it doesn’t just happen on the day. Running 3:45 takes more than gritting your teeth in the final miles. It requires smart training, careful pacing, and the confidence to hold goal pace even when fatigue sets in. The good news is that with the right plan, mindset, and a few proven strategies, a 3:45 finish is well within reach – whether you’re tackling your first marathon or chasing a new personal best.

In this guide, you’ll find everything you need to aim for that 3:45 mark:

Exact target paces and splits so you know what to hit every kilometre.
Fitness benchmarks to check if you’re ready to take it on.
A proven training plan with the sessions you need to build speed and endurance.
Race-day tactics to pace yourself smartly and finish strong.
Expert tips and real success stories from coaches and runners who’ve cracked 3:45 themselves.

No more guesswork. Just straightforward, practical guidance to help you train with confidence, run smart on the day, and enjoy the process along the way.
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Ready? Let’s go make that 3:45 marathon happen.

What Does It Take to Run a 3:45 Marathon?

To run a marathon in 3 hours 45 minutes, you need to lock into a steady pace of about 8 minutes 35 seconds per mile, or 5 minutes 20 seconds per kilometre. That rhythm has to hold mile after mile, kilometre after kilometre, without drifting too far off target.

Put another way, each 10K needs to come in just under 53 minutes, with halfway reached in about 1 hour 52 minutes.

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It sounds straightforward on paper, but the reality is tougher. As fatigue builds in the later stages, holding that pace takes more than just endurance – it demands efficient training, mental strength, and the confidence to settle into your goal rhythm from the start.

Who is this goal realistic for?

If you’re already running half marathons around 1:45–1:50, you’re in a good position to take on a 3:45 marathon with the right plan. It means you’ve built a strong aerobic base and have experience holding a solid pace over long distances. From here, the focus shifts to building long-run endurance, developing pacing control, and practising nutrition strategies for race day.

And if your PBs are a little outside that range? Don’t worry – many runners surprise themselves when they follow a structured plan. With smart training and consistency, you can turn that 8:35 per mile pace into something that feels sustainable all the way to the finish line.

Are You Ready for a 3:45 Marathon?

Before you dive into chasing a 3:40 marathon, it’s smart to check whether your current fitness is in the right range. The last thing you want is to push too hard too soon and end up frustrated or injured. Use these simple benchmarks to see if you’re ready to train for 5:20/km pace with confidence.

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Benchmark Sessions

1. The 3 x 5K Repeats Test‍

Head to a track, trail, or flat road and run 3 x 5K repeats with 5–6 minutes of light jogging or walking in between.

Aim to average close to 26–27 minutes for each 5K.
If you can finish all three feeling strong (and could imagine squeezing out another), you’re likely ready to handle marathon pace on race day.

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2. The 10K Time Trial‍

Another option is to run a controlled 10K effort.

Warm up well, then run hard but steady for the full distance.
If you can run around 52 minutes and still feel like you had a little left, that’s a strong indicator you’re on track for a sub-3:45.

These sessions give you a realistic picture of whether you have the mix of speed and endurance to train for this goal, or if you’d benefit from building a bit more base first.

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Check Your Weekly Mileage Base

Speedwork alone won’t prepare you for a marathon. You need a solid aerobic foundation to handle long runs, recover between workouts, and keep your form strong late in the race.

As a guideline:

You should already feel comfortable running 35–45 km (22–28 miles) per week for at least 6–8 weeks.
If your current mileage is lower, spend time gradually building up before layering in tougher sessions.
A steady mileage base plus regular strides or light pickups will prepare your body to handle marathon training and help you stay injury-free.

Key Training Principles

To run a marathon in 3 hours 45 minutes, your training should balance endurance, steady pacing, and strength. It’s not about hammering every run, but about putting together consistent, smart sessions that build fitness without breaking you down. Here are the key pillars to focus on each week:

1. Build Mileage Gradually

A strong aerobic base is essential for the marathon. It gives you the stamina to maintain pace late in the race and helps your body adapt to the training load.

Aim to build towards 55–65 km (35–40 miles) per week if you’re targeting sub-3:45.
Increase volume steadily, keeping jumps to no more than about 10% per week.

Most of your running should be at an easy, conversational pace. Save your energy for quality workouts.

2. Include Intervals

Intervals sharpen your speed and efficiency, making goal pace feel more natural. They also improve your ability to deal with fatigue.

Sessions like 800m or 1 mile repeats at 10K to half marathon pace work well.
Always start with a good warm-up, and jog or walk between reps for recovery.

One interval session a week is enough for most marathoners.

3. Add Tempo Runs

Tempo runs are a cornerstone of marathon prep. They help you sustain a faster pace for longer by boosting your lactate threshold.

Run these at a strong but controlled effort, close to half marathon pace.
A good target is 30–40 minutes at tempo after a warm-up.

These runs train your body to stay efficient even when the pace feels tough.

4. Don’t Skip the Long Run

Your long run is the most important session of the week for marathon training. It builds endurance, mental toughness, and teaches your body to use fuel efficiently.

Work up to long runs of 18–20 miles (29–32 km).
Keep them mostly easy, but include sections at or near marathon pace as you get closer to race day.

Think of them as practice runs for pacing, nutrition, and mindset.

5. Strength & Mobility Work

Strong, stable muscles keep you efficient and reduce the risk of injuries that can derail your training.

Focus on core stability, glutes, hamstrings, and single-leg strength.
Add mobility drills to keep hips, calves, and hamstrings loose.
1–2 short sessions a week is plenty - even 20 minutes at home can make a difference.

Pacing & Race-Day Strategy

As you step onto the start line, your plan matters just as much as your fitness - and the right pacing strategy can carry you all the way to a 3:45 breakthrough. Here's how to set it up:

1. Warm Up Properly

A proper warm-up sets you up to settle into marathon pace smoothly instead of feeling heavy or tight in the first few miles.

Easy Jog: Do 10–15 minutes of light running to get your legs moving and your heart rate up.
Dynamic Stretches: Add movements like leg swings, lunges, or hip circles to loosen up your hips and legs.
Strides: Finish with 4–5 short bursts at just quicker than marathon pace (around 80–90% effort) to wake up your stride.

By the time you reach the start line, you should feel loose, switched on, and ready for the miles ahead.

2. Start Smart

The adrenaline of race day can make you rush out too quickly, but nothing derails a marathon goal faster than spending too much energy early.

Stick to your goal pace: about 8:35 per mile or 5:20 per km.
The opening 3–5 miles should feel almost too comfortable - like you’re holding back a little.

If those splits feel relaxed, that’s exactly what you want. The marathon only starts to bite later on.

3. Hold Your Nerve in the Middle

The middle stages, particularly miles 13–20, are where focus is tested. Energy dips and the distance can feel endless if you let your mind wander.

Posture matters: stay tall, keep your shoulders relaxed, and use your arms to keep rhythm.
Find your flow: aim for smooth, steady strides instead of forcing speed.

If you can, tuck in with a group or another runner at a similar pace to help lock you into rhythm.

4. Nail the Final 10K

The last stretch is where races are won or lost against your goal time. With about 6 miles to go, it’s all about resilience.

Choose a landmark or mile marker a little way ahead and run to that, breaking the final distance into chunks.
With 2-3 miles left, it’s time to dig deep and push whatever you’ve got left.

Keep your eyes up, focus forward, and drive for the finish. Every second matters here.

Mental Tips for Breaking 3:45

Running 26.2 miles at goal pace is as much about mindset as it is about fitness. Your training gives you the physical ability, but it’s your head that keeps you steady when the distance starts to feel overwhelming. Here’s how to sharpen your mental game:

Break the Race into Sections‍

Don’t think of the marathon as one huge distance. Split it into manageable blocks and give each part its own focus:

Miles 1-6: Settle in. Relax into your pace and let the race come to you.
Miles 7-13: Stay smooth. Keep it controlled and resist the urge to push too soon.
Miles 14-20: Hold strong. This is where you’ll need focus to stay consistent.
Miles 21-23: The grind. Everyone feels fatigue here, so remind yourself you’ve prepared for this.
Miles 24-26.2: All in. Push through the last stretch and give it everything you’ve got.

Breaking the race down like this makes 26.2 miles feel far less daunting.

Use Positive Mantras‍

A simple phrase can be a powerful tool when the miles start to feel heavy. Repeat short, steady words in time with your stride:

“Relax and flow.”
“Strong and steady.”
“One mile at a time.”

These keep your mind calm and stop negative thoughts from taking over.

Control Your Breathing‍

Your breathing can anchor you when fatigue hits. Aim for a steady rhythm, such as in for three steps, out for two. It helps maintain focus, keeps tension away, and prevents panic breathing late in the race.

Visualise Success‍

In the build-up, spend time imagining yourself racing well. Picture holding pace comfortably, staying strong through the tough miles, and powering down the finishing straight. Picture the clock showing 3:45:xx as you cross the line. Having that mental image can give you a huge lift on race day.

Nutrition & Gear for a 3:45 Marathon

For a marathon, what you eat, drink, and wear can have just as much impact as your training. Keeping things simple and familiar means you’ll run with confidence and avoid any unwanted surprises on race day.

The Night Before‍

Your preparation starts with dinner the evening before:

Have a carb-based meal such as pasta, rice, or potatoes paired with lean protein.
Keep the portion moderate so you feel satisfied but not uncomfortably full.
Stay hydrated throughout the day, but avoid drinking large amounts of water just before bed.

Race Morning‍

What you eat before the race can make the difference between steady energy and mid-run stomach issues:

Go for an easy-to-digest breakfast you’ve used in training – a banana, toast with honey, or a small bowl of cereal.
Aim to eat 2–3 hours before the start, then sip water up to the line.
Avoid anything heavy, greasy, or new on the day itself. Stick to what your stomach already knows works.

Gear: Light and Familiar‍

Clothing and shoes won’t make you faster on their own, but the wrong choices can ruin your race:

Pick marathon shoes you’ve tested in training and know feel good over long miles.
Wear kit you’ve already logged long runs in – new socks or shorts are a gamble not worth taking.
Check the weather the day before and dress accordingly. Layers can be useful for the wait at the start, but make sure you’re in your race kit when the gun goes.

Frequently Asked Questions

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