How to Calculate the Right Amount of Carbs for Your Training
Why Carbs Matter For Runners
When it comes to fueling your body for running, carbohydrates are the backbone of endurance, speed, and stamina.
Whether you’re heading out for a casual jog along the beach or training for your next half marathon, knowing how much carb you need, and when to eat it, can be the difference between hitting your stride or hitting the wall.
But how do you work out exactly how much carb your body needs? It’s not a one-size-fits-all approach. It depends on your body size, the intensity and duration of your training, and your personal performance goals.
Why Carbs Matter For Runners
Carbs are your body’s preferred source of energy during exercise. As you run, your muscles rely heavily on glycogen, the stored form of carb found in your muscles and liver.
The problem is, your glycogen stores are limited. For most people, they last between 90 minutes and two hours of moderate to high-intensity exercise. Once you run out, you can feel heavy-legged, sluggish, and mentally foggy aka hitting the wall.
Getting your carb intake right not only helps you avoid that crash, but also improves endurance, reduces fatigue, supports recovery, and boosts mental sharpness.
Step 1: Know Your Training Load
Understand your training load. Are you running a few days per week? Or are you doing long runs, intervals, and hill sprints most days? The following is a rough guide developed by sports nutrition experts to help you estimate what you need:
- Light training (low intensity): 3-5g of carbs p/kg of body weight per day
- Moderate training (1 hour/day): 5-7g p/kg per day
- High volume endurance training (1-3 hours/day): 6-10g p/kg per day
- Extreme training (>4 hours/day): 8-12g p/kg per day
If you weigh 70kg and are training at a moderate level, you’ll need roughly 350–490g of carbs per day.
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Step 2: Tailor It
Are you training for fat loss, improved performance, or simply staying energised for daily runs?
If it’s weight loss, you might be tempted to cut carbs, but doing so can compromise your performance and recovery. Instead, time your carbs smartly – more around your workouts and less during periods of rest.
If it’s performance gains at high intensities or distances over 10km, a consistent and slightly higher carb intake will be beneficial. On the other hand, for recovery runs or rest days, slightly lower intakes can be appropriate.
Step 3: Distribute Your Carbs
Not all carbs are equal, and when you eat them matters just as much as how much. Here’s how to think about it across the day:
- Before your run: Aim for a carb-rich meal 2-3 hours before, like porridge with fruit or a wholegrain sandwich with banana. If you’re eating within an hour of your run, go for something lighter like toast with honey or a sports drink.
- During your run (for sessions longer than 90 minutes): You’ll need 30-60g of carbs per hour. That could look like a gel every 30-45 minutes or sipping on a sports drink.
- After your run: Replenishing glycogen is key. A mix of carbs and protein (Greek yoghurt with fruit, a smoothie with almond milk and oats, or a chicken and rice meal) will help recovery.
Step 4: Choose The Right Carb
Focus on low glycaemic index (GI) carbs like wholegrains, legumes, vegetables, and fruit for your day-to-day fuel. These provide slow-release energy, stabilise blood sugar and keep you feeling steady.
Before and during runs, higher GI carbs like ripe bananas or sports drinks are better because they digest quickly and give you an immediate boost.
Don’t forget fibre, either, as it supports gut health and helps regulate energy. But go easy on fibrous foods immediately before a run to avoid stomach discomfort.
Step 5: Adjust For Experience
Some runners find they perform better with slightly fewer carbs, especially if they’re metabolically efficient. Others need more to feel and perform their best. Trial, error, and a bit of tracking can help you land on your sweet spot.
Carbohydrates are not your enemy. They’re your running ally.
Fuelling properly is one of the most underrated performance enhancers available to any runner. And the best part? It’s entirely within your control. No fancy supplements required. Just smart, everyday choices on your plate.
INSIDER KNOWLEDGE: Jake Biggs is a sports nutritionist who lives and breathes running, literally! As a lifelong runner, he knows exactly what fuels performance, recovery, and stamina, all from personal experience. Obsessed with giving runners that nutritional edge, you’ll find Jake reading journal articles instead of watching marathons. Carbs over couch, always!
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