Glycogen Storage Capacity

About this calculator

Muscle glycogen is the body’s stored form of carbohydrate, packed into muscle fibers as branched glucose chains ready to fuel contraction. Research on muscle biopsies puts typical storage at roughly 12 to 15 grams of glycogen per kilogram of muscle mass in a well-fed, moderately trained person, though the ceiling rises meaningfully with endurance training and can be pushed further with carbohydrate loading.

Endurance athletes track glycogen capacity because it caps how long they can sustain hard efforts before “hitting the wall” — marathon runners and long-distance cyclists plan carb-loading protocols in the days before a race specifically to maximize this store, since each gram of glycogen carries roughly 4 kilocalories of accessible energy (plus the water bound to it, which is why loading also adds noticeable weight). Sports dietitians use rough capacity estimates like this one to explain why a bigger, more muscular athlete can carry meaningfully more fuel than a smaller one at the same training level.

Enter your muscle mass in kilograms and this calculator multiplies it by a fixed 15 grams per kilogram, the top of that range, to estimate your total glycogen storage capacity in grams, along with the energy it represents in kilocalories; a less well-fed or less trained person may store somewhat less. Trained, well-fed endurance athletes typically store more: about 150 mmol per kg of wet muscle (roughly 24 g/kg), and up to about 200 mmol/kg (around 32 g/kg) after a few days of high-carbohydrate eating (Murray and Rosenbloom, Nutrition Reviews, 2018), so for them the result is an underestimate.