How Many Carbs Per Hour Cycling – The Science of 30-120g/h

How many carbs per hour do you need for cycling? The short answer is 30-120 grams per hour, depending on duration and intensity. But the science behind these numbers is fascinating—and understanding it will help you fuel smarter.

Get your personalized carbohydrate targets with our Cycling Race Nutrition Calculator.

The Quick Answer: Carb Intake Guidelines

Ride Duration	Carbs Per Hour	Carb Strategy
Under 45 min	0g (or mouth rinse)	Not needed
45-75 min	0-30g	Small amount optional
1-2 hours	30-60g	Single carb source OK
2-2.5 hours	60-90g	Multiple transportable carbs
2.5-3+ hours	80-120g	Multiple transportable carbs essential

These guidelines are based on decades of research by sports scientists including Dr. Asker Jeukendrup, whose work revolutionized our understanding of carbohydrate oxidation during exercise.

Why Carbs Matter During Cycling

Your Body's Fuel Tanks

Your body stores carbohydrates as glycogen in two locations:

Storage Location	Approximate Capacity	Availability
Muscle glycogen	300-400g	Direct use during exercise
Liver glycogen	80-100g	Maintains blood glucose
Blood glucose	~5g	Immediate fuel

Total: approximately 400-500g of stored carbohydrate

At high intensities (above 60-70% VO2max), carbohydrates become your primary fuel. A cyclist working at race pace might burn 1-2g of carbs per minute—meaning glycogen stores last only 90-150 minutes at best.

What Happens When You Run Low

When glycogen depletes, you experience what cyclists call "bonking" or "hitting the wall":

• Sudden fatigue
• Inability to maintain power
• Poor concentration
• Mood changes
• Shaking or weakness

External carbohydrate intake prevents this by providing fuel directly, sparing your limited glycogen stores.

The Science of Carbohydrate Absorption

Intestinal Transporters

Here's where it gets interesting. Your small intestine uses specific transport proteins to absorb different sugars:

SGLT1 Transporter:

• Absorbs glucose, maltose, maltodextrin
• Maximum capacity: ~60g per hour
• This is why "single carb source" intake peaks at 60g/h

GLUT5 Transporter:

• Absorbs fructose only
• Maximum capacity: ~30g per hour
• Works independently of SGLT1

The Multiple Transportable Carbohydrates Discovery

Research showed that combining glucose and fructose uses both transport systems, dramatically increasing total absorption:

Carb Strategy	Max Oxidation Rate	Best For
Glucose only	~60g/hour	Events under 2.5 hours
Maltodextrin only	~60g/hour	Events under 2.5 hours
Glucose + Fructose (2:1)	~90g/hour	Events 2.5-4 hours
Glucose + Fructose (1:0.8)	~100-120g/hour	Ultra events, trained guts

Key insight: To exceed 60g/hour intake without GI distress, you MUST use multiple transportable carbohydrates (typically glucose/maltodextrin + fructose).

The Optimal Glucose:Fructose Ratio

Research has evolved on this topic:

• Original recommendation: 2:1 glucose to fructose
• Current thinking: Ratios from 2:1 to 1:0.8 work well
• Many commercial products: Now use closer to 1:0.8 ratio

The exact ratio matters less than including both types of carbohydrates.

Does Body Mass Affect Carb Needs?

Surprisingly, body mass has minimal impact on carbohydrate needs during cycling.

Why Weight Doesn't Matter Much

The limiting factor is intestinal absorption capacity, which doesn't scale significantly with body size. A 60kg rider and a 90kg rider have similar gut absorption limits.

Factor	Scales with Weight?	Impact on Carb Needs
Glycogen stores	Somewhat	Minor
Gut absorption	No	Major limiting factor
Oxidation capacity	Minimal	Relatively fixed
Calorie burn rate	Yes	Affects total needs

Practical Implication

A 60kg climber and 90kg sprinter doing a 3-hour race should target similar carb intake per hour (80-90g). The heavier rider burns more total calories but can't absorb carbs any faster.

Exception: Pre-race nutrition (carb loading, pre-race meal) is often expressed per kg body weight because glycogen storage does scale with muscle mass.

Carbs by Duration: Deep Dive

Under 45 Minutes

Target: 0g (mouth rinse optional)

For short, high-intensity efforts, you have enough glycogen. However, research shows that even rinsing your mouth with a carb solution can improve performance—your brain senses carbs and reduces perceived effort.

Practical application:

• Nothing needed for most riders
• Mouth rinse might help for all-out efforts
• Stay hydrated

45-75 Minutes

Target: 0-30g total

You're unlikely to deplete glycogen in this timeframe, but a small amount of carbs can help:

• Maintain blood glucose
• Provide psychological benefit
• Prepare you if the effort extends longer

Practical application:

• One gel or 500ml sports drink is sufficient
• Not essential for trained athletes
• More important if you skipped pre-ride nutrition

1-2 Hours

Target: 30-60g per hour

Now carbohydrates become performance-relevant. Glycogen depletion becomes possible, especially at high intensities.

Practical application:

• Single carb source products work fine (gels, sports drinks)
• Start fueling in the first 20-30 minutes
• Aim for consistent intake rather than large boluses

Example fueling (90-minute race):

Time	Fuel	Carbs
0:00	Start with sip of sports drink	10g
0:20	Gel	25g
0:45	300ml sports drink	20g
1:10	Gel (if needed)	25g
Total		~80g (53g/h)

2-2.5 Hours

Target: 60-90g per hour

Multiple transportable carbohydrates become beneficial. Single-source intake limits you to ~60g/h, leaving performance on the table.

Practical application:

• Choose products with glucose/maltodextrin + fructose
• Mix gels and sports drinks
• Practice this intake level in training first

2.5-3+ Hours

Target: 80-120g per hour

Maximum fueling for maximum performance. This requires:

1. Multiple transportable carbohydrates
2. Gut training (practice at this level)
3. Careful product selection
4. Optimal timing

Practical application:

• Use specifically designed high-carb products
• Combine drinks, gels, and possibly solid food
• Very consistent intake timing (every 15-20 minutes)
• Have tested extensively in training

Gels vs Drinks vs Solid Food

Different carb sources have pros and cons:

Energy Gels

Pros	Cons
Convenient, portable	Need water to consume
Precise dosing	Can cause GI issues
Fast absorption	Texture not for everyone
Easy during intense efforts	Often expensive

Best for: Racing, high-intensity efforts, quick energy needs

Sports Drinks

Pros	Cons
Combined hydration + carbs	Limited by bottle capacity
Easy to consume	Hard to increase carb concentration
Customizable concentration	May need additional gels
Generally well tolerated	Flavor fatigue on long rides

Best for: Balanced hydration and fueling, moderate carb needs

Solid Food (Bars, Rice Cakes, Real Food)

Pros	Cons
More satisfying	Slower absorption
Variety helps with long events	Hard to eat at high intensity
Often cheaper	Requires chewing
Can include other nutrients	Potential GI issues

Best for: Long, steady endurance rides; lower intensity; variety

Mixing Sources

Most athletes benefit from combining sources:

Example mix for 4-hour gran fondo (targeting 80g/hour):

• Bottles: 60g carbs per hour (via concentrated drink mix)
• Gels: 1 per hour = 25g
• Backup bars: As desired at rest stops

Common Mistakes

Mistake 1: Starting Too Late

Carbs consumed in the first 30 minutes still benefit you later. Don't wait until you feel tired—by then you're already behind.

Mistake 2: Too Much, Too Fast

Dumping 60g of carbs into an untrained gut causes GI distress. Build up gradually in training.

Mistake 3: Single-Source for Long Events

If you're doing 3+ hours and using only glucose-based products, you're limited to 60g/h. Switch to multiple transportable carbs.

Mistake 4: Ignoring Individual Tolerance

Some people tolerate high carb intake naturally; others need weeks of gut training. Test your limits in training.

Mistake 5: Not Practicing

Race day is not the time to try 100g/hour for the first time. Practice your exact plan in training.

How to Increase Your Carb Tolerance

If you currently struggle with high carb intake, you can train your gut:

Week 1-2: Baseline

• Use your current comfortable intake
• Note any GI issues
• Typically start around 40-60g/hour

Week 3-4: Small Increase

• Add 10g per hour to your training rides
• Practice the same products you'll race with
• Monitor tolerance

Week 5-6: Build Further

• Continue adding 10g per hour if comfortable
• Now at 60-80g/hour range
• Focus on consistency

Week 7-8: Peak Adaptation

• Reach your target race intake (80-90+ g/hour)
• Practice in race-like conditions
• Fine-tune timing and products

Most athletes can significantly increase tolerance within 2-4 weeks of consistent practice.

For a complete protocol, see How to Train Your Gut for Cycling.

Key Takeaways

1. Duration determines needs: 30-60g/h for 1-2 hours, 60-90g/h for 2-3 hours, 80-120g/h for 3+ hours
2. Multiple transportable carbs unlock intake above 60g/hour
3. Body mass doesn't limit carb absorption—gut capacity does
4. Start early in your ride—don't wait until you're depleted
5. Practice everything in training before racing

Get Your Personalized Numbers

Use our Cycling Race Nutrition Calculator to get specific carbohydrate targets based on your race duration, type, and strategy preferences.

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Related Articles

• Cycling Race Nutrition Guide - Complete nutrition overview
• How to Train Your Gut for Cycling - Increase carb tolerance
• Energy Gels vs Real Food for Cycling - Choosing carb sources
• Cycling GI Issues - Preventing stomach problems