The Complete Guide to Carb Loading: How Many Carbs Per Kg Before Your Race

The pasta dinner is where a lot of race nutrition plans go to die.

Not because pasta is bad. Pasta is fine. But one heroic bowl of noodles at 7pm does not magically refill every glycogen tank in your body, especially if you spent the previous week under-eating because taper hunger got weird.

Carb loading works, but only when you treat it like a body-weight target instead of a vibe. The number that matters is grams of carbohydrate per kilogram of body weight per day.

The boring answer for most endurance athletes is 8-10 g/kg/day for the final 24-48 hours before a long race. For very long events, some athletes push closer to 10-12 g/kg/day. That is a lot of carbs. It is also why the plan has to be boring, low-fiber, and practiced.

This is where people get two birds stoned at once: they top off glycogen and accidentally test whether their stomach can handle 600 grams of carbs the day before an A race. Buddy, test that part before race week.

Carb loading is about glycogen, not dinner theater

Your muscles store carbohydrate as glycogen. Your liver does too. During a marathon, Ironman, gran fondo, or ultra, those stores are one of the main reasons you can hold pace instead of slowly turning into a folding chair.

The goal of carb loading is simple: start the race with those stores topped off.

Burke and colleagues helped establish the modern endurance-sport approach, where athletes increase carbohydrate intake while reducing training volume before race day. The old-school depletion phase is mostly unnecessary for normal athletes. You do not need to do a monster workout, starve yourself of carbs, then panic-eat spaghetti like you are negotiating with your quads.

The more practical version is this:

• taper training volume
• increase carbohydrate for 24-48 hours
• reduce fat and fiber enough to make room
• keep protein normal
• keep foods familiar

That last part matters. Carb loading is not a food adventure. It is the culinary version of wearing the boring socks that never blister.

How many carbs per kg?

For most long endurance races, use this range:

Race situation	Carb target	When to start
Half marathon over 90 minutes	6-8 g/kg/day	24 hours before
Marathon	8-10 g/kg/day	24-48 hours before
Ironman 70.3	8-10 g/kg/day	24-48 hours before
Ironman 140.6	10-12 g/kg/day	36-48 hours before
Ultra / 100-mile ride / gran fondo	8-12 g/kg/day	24-48 hours before

The Academy of Nutrition and Dietetics, Dietitians of Canada, and ACSM position stand puts high-volume endurance athletes in the upper carbohydrate ranges when training or racing demands are high. In normal-person language: the longer the event and the harder the effort, the more useful a full tank becomes.

Here is what the math looks like:

Body weight	8 g/kg	10 g/kg	12 g/kg
50 kg / 110 lb	400g	500g	600g
60 kg / 132 lb	480g	600g	720g
70 kg / 154 lb	560g	700g	840g
80 kg / 176 lb	640g	800g	960g
90 kg / 198 lb	720g	900g	1080g

Those numbers look ridiculous the first time you see them.

But remember, you are not supposed to add all of that on top of your normal food. You shift the plate. Less salad, beans, nut butter, cheese, and giant hunks of meat. More rice, bagels, pancakes, potatoes, pretzels, applesauce, cereal, sports drink, jam, and low-fiber bread.

Average is a trap. A 50 kg athlete and a 90 kg athlete should not be eating the same carb load just because they both signed up for the same marathon.

For female athletes, the body-size point is especially important because a lot of example meal plans are quietly written around a 70-80 kg male body. A 55 kg woman targeting 8 g/kg needs about 440g of carbs, not the 700g plan some dude on Reddit copied from a pro triathlete. Hormonal phase can also affect appetite, GI comfort, and water retention for some women, so practice the bigger carb days before race week if that applies to you.

The 24-hour plan versus the 48-hour plan

You do not always need a full two-day carb load.

For a marathon, 70.3, century ride, or hard gran fondo, I like 36-48 hours because it gives you room to spread the food out. Trying to eat 700g of carbs in one day can feel like a part-time job with maple syrup on it.

For a half marathon, shorter trail race, or anything near 90 minutes, one higher-carb day is usually enough. The race is not long enough to justify turning Thursday and Friday into a cereal-based hostage situation.

For Ironman and 100-mile ultras, the bigger load makes more sense. You are not trying to fuel the whole race from stored glycogen, because that is impossible, but you want to start with every tank full before the long bike buffet or the all-day aid-station crawl begins.

And yes, carb loading can make the scale jump. Glycogen pulls water with it, often around 3 grams of water for every gram of glycogen stored. That is not fat gain. That is stored fuel plus water, which is the whole point. Do not panic because the scale is up two pounds on race morning.

Water under the fridge.

What to eat when the target is huge

The biggest mistake is trying to hit a carb target with foods that are technically healthy but practically annoying.

Beans have carbs. So does quinoa. So does a giant bowl of vegetables. But if you try to carb load on high-fiber foods, you may spend race morning conducting field research in the bathroom line.

Use low-fiber, familiar carbs:

Food	Approximate carbs
Plain bagel	45-55g
2 cups cooked white rice	90g
Large baked potato	60g
2 pancakes with syrup	80-100g
2 slices white toast with jam	55-70g
Banana	25-30g
16 oz sports drink	30-35g
Applesauce pouch	20-25g
Pretzels, 2 oz	45g
Bowl of low-fiber cereal with milk	60-90g

None of this is fancy. That is why it works.

Rice bowls, bagels with jam, pancakes, pretzels, low-fiber cereal, potatoes, sports drink, and applesauce are easier to stack than a mountain of whole-grain pasta and broccoli. Keep the protein normal, not huge. Keep fat lower than usual because fat slows digestion and takes up calories you need for carbs.

I would rather see an athlete eat boring white rice three times than force down a "perfect" meal that fights back at mile 12.

Need exact race-day numbers? Build your personalized carb, fluid, and sodium plan in about 60 seconds: Use the free EnduranceOS calculator.

A sample carb-loading day for a 70 kg athlete

Let's say you weigh 70 kg and want the middle target: 9 g/kg.

That is 630g of carbs.

Here is one way to get close without eating one mega-meal that ruins your evening:

Time	Meal	Approximate carbs
Breakfast	2 bagels with jam, banana, orange juice	170g
Snack	Pretzels and sports drink	75g
Lunch	White rice bowl with chicken, small amount of sauce, applesauce	150g
Snack	Low-fiber cereal with milk, honey	90g
Dinner	Pasta or potatoes with lean protein, low-fiber bread	120g
Before bed	Sports drink or graham crackers	30-50g

That lands around 635-655g, depending on portions.

For a 55 kg athlete, the same structure might be closer to 450-500g: one bagel instead of two, smaller rice portions, less sports drink. For an 85 kg athlete, the opposite is true. You may need bigger portions or more liquid carbs because chewing your way to 850g is a lot of mouth labor.

Liquid carbs help. Sports drink, juice, Maurten Drink Mix, Skratch High Carb, maple syrup in oatmeal, or even a normal soda with dinner can make the total easier. I know the internet gets weird about sugar, but race week is not the time to win a clean-eating contest. It is the time to show up with full glycogen and a stomach that still likes you.

What most athletes mess up

They start too late. If your plan begins with dinner the night before, you are probably short. Start at breakfast the day before at minimum. For longer races, start two mornings out.

They eat too much fiber. Vegetables, beans, bran cereal, giant salads, chia seeds, and high-fiber wraps can all be useful foods. Just not right before you ask your gut to behave for four hours.

They forget sodium. Carb loading pulls in water, and pre-race nerves can make people drink like they are trying to win hydration. Add some sodium through normal salty foods, broth, pretzels, sports drink, or electrolyte mix. Do not just pound plain water all day. The sodium guide covers the race-day side of that math.

They try to diet during taper. This is common. Training volume drops, hunger gets strange, and people get twitchy about eating more while running less. But the taper is when you absorb training and fill the tank, not when you audition for a smaller race kit.

They confuse carb loading with race fueling. A carb load helps you start full. It does not remove the need to eat during the race. If you are racing longer than 90 minutes, you still need a during-race carb plan. The gel timing guide and glucose-to-fructose guide pick up where this article stops.

The gel is not the plan. The grams are the plan. Same idea here.

Race-by-race tweaks

Half marathon. If you will finish under 90 minutes, a normal high-carb dinner and breakfast may be enough. If you are closer to two hours, use a lighter one-day load around 6-8 g/kg. The half marathon fueling post explains where the line usually sits.

Marathon. This is the classic carb-load race. Use 8-10 g/kg/day for 24-48 hours, then eat your race breakfast 2-4 hours before the start. The pre-race breakfast guide covers that final meal.

Ironman 70.3. Use marathon-style loading, then remember the race is one awkward swim, one long bike buffet, and one half marathon where your stomach starts making executive decisions. Keep the pre-race load simple, then get most of your fuel on the bike.

Ironman 140.6. Go closer to 10-12 g/kg/day if you have practiced it. Start 36-48 hours out. You still need the Ironman carb plan once the race starts, but the carb load gives you a better opening hand.

Ultra and 100-mile events. Carb loading still helps, but ultra intensity is lower and GI comfort matters more. I would rather see 8-10 g/kg done cleanly than 12 g/kg done with bloating, panic, and three new foods. For 50K racing, the 50K fueling guide is the better during-race companion.

Century rides and gran fondos. Carb loading matters because the late climbs get rude. Use 8-10 g/kg, keep breakfast familiar, then start eating early on the bike. The gran fondo nutrition guide covers bottle setup and aid-station strategy.

Practice the load before race week

This is the part nobody wants to do because it feels silly.

Practice your carb load before a long race simulation. Pick a weekend with a big long run or ride. Do a one-day mini-load at 7-8 g/kg, eat the same breakfast you plan to use, then see what happens.

Did you feel springy or heavy? Did your stomach behave? Did the scale jump in a way that made you irrationally angry even though you knew it was water? Good. That is useful information.

Then adjust.

Maybe you need more liquid carbs. Maybe pancakes work better than pasta. Maybe two big meals feel worse than five smaller hits. Maybe dairy is fine at rest but dicey before a long run. That is all better to learn in training than at 4am in a hotel room while your race bib is judging you from the desk.

This does not need to become a spreadsheet cult. But you do need a plan simple enough that you can still follow it when travel, nerves, expo snacks, and group-dinner chaos start making decisions for you.

Carb loading fills the tank. Race fueling keeps the engine from draining it.

The EnduranceOS planner builds a personalized, hour-by-hour fueling plan based on your race, your body, and your conditions. It takes about 60 seconds, and it is free.