Carb Loading Calculator

Carb loading is how you walk to the start line with full glycogen stores instead of half-empty ones. For any event past about 90 minutes, the carbs you eat in the 24-48 hours before matter more than anything you do that morning. The calculator above turns your body weight and a loading intensity into total daily carb grams plus a rough per-meal split.

What carb loading is

Muscle glycogen is your fast fuel. It runs low in long efforts, and topping it off ahead of time buys you more time before you fade. The amount you need scales with body weight, so the calculator works in grams per kilo per day.

• Moderate (8 g/kg/day): a solid top-off for a half marathon, an Olympic triathlon, or a long ride.
• High (10 g/kg/day): for marathons, 70.3 distance, and events you expect to push past three hours.
• Max (12 g/kg/day): the upper end, for full Ironman, ultras, and anything where glycogen is the limiter.

A 70 kg athlete on the high setting needs 700g of carbs that day. That is a real number, and it is more than most people eat without planning for it.

Reading your result

The calculator gives you the daily total and divides it by five for a per-meal target. For that 70 kg athlete at 700g, each meal lands near 140g. Spread it across the day so you are not forcing down a single mountain of pasta at dinner.

Lean on carbs your gut handles fast: white rice, white bread, pasta, bananas, oats, sports drink, a little jam. Cut fibre and fat down for these two days. They slow digestion and leave you bloated at the line, which is the opposite of what you want.

The water weight is the point

You will gain 1-2 kg over a loading block. That is not fat. Every gram of stored glycogen pulls roughly 3 grams of water in with it, so a full tank shows up on the scale and in how your legs feel the morning of. Do not panic and skip the loading because the number went up. The weight is the fuel.

The common mistake is testing this for the first time on race day. Practice your loading and your in-race fuelling in training so your gut is ready for the volume. For how to build that tolerance, read the gut training and carb tolerance guide.