What is bonking in cycling?

Bonking (or hitting the wall) occurs when glycogen stores are depleted. Symptoms include sudden fatigue, dizziness, inability to maintain power, confusion and sometimes nausea. It feels like your legs are made of concrete.

How long can I ride without eating?

For most trained cyclists at moderate intensity, glycogen lasts 90-120 minutes. At race pace, stores deplete in 60-90 minutes. Easy riding can be sustained for 2-3 hours without food.

How do I prevent bonking?

Start fuelling from the first hour: aim for 30-60g of carbs per hour (60-90g for trained riders in long events). Eat before you feel hungry — by the time you feel depleted, it is too late.

Does carb loading help?

Yes. Proper carb loading (8-10g/kg/day for 2-3 days before an event) can increase glycogen stores by 50-100%, significantly delaying the bonk point.

Can you recover from a bonk during a ride?

Yes, but slowly. Consume fast-acting carbs (gels, sugary drinks, sweets). It takes 15-30 minutes to feel the effect. You will not fully recover to normal performance during the ride.

BikeCalcs

Bonk Calculator — When Will You Hit the Wall?

Estimate when glycogen stores will deplete without fuelling during a ride.

Body Weight

Ride Intensity

Fitness Level

Hours Since Last Meal

Last Meal Size

How We Calculate This

Glycogen Depletion Model

Glycogen stores: ~1600-2500 kcal depending on fitness and body weight
Pre-ride meal adds 100-600 kcal to available glycogen
Carb burn rate varies by intensity: 35% (easy) to 90% (race) of total calories from carbs
Bonk time = Available glycogen / Carb burn rate per hour
Warning zone = 70% of bonk time (when you should definitely start eating)

Frequently Asked Questions

Related Calculators

Ride Calorie Calculator

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Hydration Calculator

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Carb Loading Calculator

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Electrolyte Calculator

Calculate sodium and electrolyte needs for long rides.

Recovery Nutrition Calculator

Calculate post-ride protein and carb intake for optimal recovery.

Last updated: February 2026

All calculations are estimates. Always verify results and consult a professional bike fitter where appropriate.