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Pre-Workout Carb Timing Calculator

Fuel your training with the right carbs at the right time.

How it is calculated

The rule is 1 g of carbohydrate per kg of body weight for each whole hour before training, up to 4 hours: carbs (g) = weight (kg) × hours before. Hours before must be 1, 2, 3 or 4, giving 1, 2, 3 or 4 g/kg; if the field is empty it defaults to 2. Energy is carbs × 4 kcal. Results are rounded to whole grams and kcal, and the g/kg figure shows one decimal. Weight must be between 2 and 650 kg. Any other timing, such as 0.5, 1.5 or 6 hours, or text in the field, shows no result instead of guessing. The figure says nothing about fat, fiber or protein in the meal.

Worked example

An athlete weighs 72 kg and will eat 3 hours before training. The rule gives 3 g/kg, shown as 3.0 g/kg. Carbohydrate = 72 × 3 = 216 g. Energy = 216 × 4 = 864 kcal. Eating only 1 hour before would give 72 g (288 kcal), so a smaller snack suits a shorter gap, while the 3-hour window has time for a full meal.

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Common mistakes

  • Typing the gap in minutes (such as 90) or as a fraction of an hour. Only the whole hours 1 to 4 are accepted; anything else shows no result.
  • Entering a gap longer than 4 hours and expecting a larger target. The scale stops at 4 g/kg, and 6 hours is refused.
  • Leaving the hours box empty and not noticing the default. An empty box is treated as 2 hours, which gives 144 g for a 72 kg athlete.
  • Eating the whole number as one snack at 1 hour out. The tool's 1-hour figure is the smaller one for that reason, so do not use a 3-hour portion near the start.
  • Entering weight in pounds. The unit is kilograms, so a 160 lb athlete is about 72 kg, and the wrong unit more than doubles the carbohydrate target.

Sources

About this calculator

Pre-workout carbohydrate timing follows guidance from sports-nutrition bodies like the International Society of Sports Nutrition and the American College of Sports Medicine, which distinguish two feeding windows. A larger meal eaten roughly three to four hours before training (about one to four grams of carbohydrate per kilogram of body weight) tops off liver and muscle glycogen and has time to fully digest, while a smaller, faster-digesting snack about an hour out (often around one gram per kilogram) raises blood glucose closer to the effort without sitting heavy in the stomach.

Endurance athletes, strength trainees, and their coaches use this kind of timing to avoid the two failure modes of pre-workout fueling: training on empty glycogen stores, which blunts high-intensity output, or eating too close to the session and inviting gastrointestinal distress from slow-digesting fat, fiber, or an oversized carbohydrate load. Cyclists, runners, and team-sport athletes in particular plan meals around this window before races or hard interval sessions.

Carbohydrate targets scale at 1 g per kilogram for each hour before training, from 1 g/kg at one hour up to 4 g/kg at four hours.

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