Running Calorie Calculator: How Many Calories Should A Runner Eat

How Many Calories Should A Runner Eat?

When you run, your body primarily burns glycogen, a fast-acting fuel stored in your muscles and liver. It also taps into fat for energy and, if you're undernourished, even breaks down protein—something you want to avoid.

Glycogen is your body’s preferred fuel source because it provides quick, efficient energy. But there's a catch: your glycogen supply is limited.

Depending on your body size and muscle mass, you can store only 1,400 to 2,000 calories of glycogen—roughly 1 to 2 hours of running before you run out.

What Happens When You Run Out of Glycogen?

You hit the wall—also known as bonking—where your energy levels plummet, and your legs feel like lead. The good news? You can prevent bonking with proper fueling.

How Many Calories Should You Consume While Running?

To maintain energy levels and keep your performance strong, aim to replenish 25-35% of the calories you burn per hour. Nearly all of these calories should come from carbohydrates, which are the most efficient energy source for endurance running.

Why Energy Gels?

Energy gels are designed to deliver fast, efficient carbohydrates while you're on the move. Unlike fats or proteins, which take longer to digest, carbohydrates provide quick energy—helping you maintain endurance and avoid sluggishness.

Consuming too much fat or protein mid-run can slow digestion, leading to anything from delayed energy release to full-blown digestive distress—something no runner wants on race day.

That’s why MUIR Energy Fast Burning Gels, like Red Raspberry, are crafted to maximize carbohydrate absorption while being gentle on the stomach. Plus, they’re made with real ingredients, so you get natural, effective fuel—without the artificial aftertaste. 

Calculating Running Calories Per Hour

To optimize your fueling strategy, enter your weight and average pace to estimate how many calories you should consume per hour while running.

Important: Gradually increase your calorie intake over multiple runs to help your digestive system adjust. Start with short, easy runs, then progressively increase calories, intensity, and duration as your body adapts.

Example Nutrition Strategy

A 150-pound runner with a 10:00 min/mi pace burns approximately 668 calories per hour. To maintain energy levels, they should aim to consume 167-234 calories per hour (25-35% of calories burned).

Want to know more about how to create your own running nutrition plan? Get our training guide here.