How to Fuel Your Next Race: Carbs, Timing & the Science Behind Endurance Performance

Let’s get one thing straight—you don’t need to bonk at mile 18 or fade halfway through your ride. If your tank runs empty mid-race, it’s not about toughness—it’s about fueling. And smart athletes don’t wing it...they calculate it.

That’s where this Race Fueling Calculator comes in. Designed using research-backed guidelines from the International Society of Sports Nutrition (ISSN) and other top sports science sources, it gives you personalized recommendations on how many grams of carbohydrates per hour you need based on your body weight, race duration, and intensity.

Why Carbohydrates Matter for Performance

Carbohydrates are the body’s most efficient energy source during endurance exercise. Stored as glycogen in your muscles and liver, they fuel your movement, power your pace, and keep your brain sharp. But there’s a catch—your glycogen stores are limited. Most people have enough for about 90–120 minutes of moderate to hard effort.

After that? If you’re not fueling, performance tanks. Fatigue skyrockets. Your pace drops. You bonk.

That’s why taking in carbs during long efforts is crucial. It maintains blood glucose, spares muscle glycogen, and helps you go harder, longer, and faster.

How Many Carbs Should You Take In Per Hour?

According to the ISSN’s 2017 position stand on nutrient timing, your hourly carbohydrate needs depend on your training intensity and duration:

• 👟 Low Intensity: ~30g/hour (easy pace, short efforts)
• 🏃 Moderate Intensity: ~60g/hour (tempo runs, long rides)
• 🔥 High Intensity / Race Pace: ~90g/hour (marathons, triathlons, threshold work)

To absorb 90g/hour, you'll need a mix of glucose and fructose (2:1 ratio) to maximize uptake without GI distress. That’s why high-carb fueling powders like our GlycoFuel use dual-source carbs.

How to Use the Race Fueling Calculator

Here’s how it works:

1. 💪 Enter your body weight in pounds
2. ⏱️ Input your estimated race duration in hours
3. 🔥 Select your intensity level
4. 📊 Get your carb needs per hour and total intake calculated instantly

When Should You Start Fueling?

Ideally, begin within the first 30–45 minutes of your race—before fatigue sets in. After that, fuel every 15–30 minutes to keep blood glucose steady and energy up. Waiting until you feel tired is too late.

Simple fueling guide:

• Start early: 15–30g within the first 30 minutes
• Continue: 20–30g every 30 minutes (or ~60g/hour)
• For high-intensity or long events: push to 90g/hour with dual-carb sources

Other Factors to Consider

Hydration, sodium, and gut training all impact your fueling strategy. If you’re taking in more than 60g/hour, you’ll want to practice that in training and make sure your gut is ready.

Pair carbs with electrolytes like the 3:2 sodium-potassium blend found in our Quench Hydration for optimal absorption and reduced cramping.

TL;DR – Race Fueling 101

• 💣 You’re not bonking—you’re underfueling
• 🍌 Aim for 30–90g of carbs per hour based on effort
• 📱 Use our calculator to dial in your exact needs
• 🧪 Train your gut and practice your strategy before race day

Ready to race smart? Use the calculator and fuel like a pro.