Carb loading calculator for cycling: days × grams × your weight
For road, gravel & Zwift races · protocol · food translation · four classic mistakes · the scale truth
Every carb-loading guide on the internet was written for marathoners. Cyclists got the pasta-party folklore. The protocol itself is simple arithmetic — one to two days, eight to ten grams of carbohydrate per kilo of body weight, easy legs — and it's worth free minutes in any race longer than ninety. This calculator does the arithmetic and then translates it into actual food.
How do you carb load properly?
Raise carbohydrate intake to 8–10 g per kg of body weight per day for the 1–2 days before your event while cutting training right back. Muscles stock glycogen above their normal level — supercompensation. The old deplete-then-load weeks are obsolete; short and disciplined wins.
What's happening inside (supercompensation without the folklore)
Trained legs and liver hold roughly 400–600 g of glycogen — about 2,000 kJ of race-grade energy. Take the training stress away, push carbohydrate in, and muscle overstocks beyond its everyday level. Modern protocols dropped the brutal depletion phase decades ago: for trained athletes, one to two committed days do the whole job.
And the part nobody warns you about: each gram of glycogen locks in about 3 g of water. Load 200 extra grams and the scale jumps by well over a kilo overnight. That weight IS the proof of a successful load — it's bottled energy, and it's gone before the first hour is done. Panicking and under-eating on race morning is how riders un-load.
What 630 grams looks like as food
Grams are an abstraction; breakfast isn't — the calculator above turns your number into a day of actual food.
A 70 kg sample day (~630 g): breakfast — big bowl of porridge, banana, maple syrup (~120 g) · mid-morning — litre of diluted juice, toast and jam (~105 g) · lunch — large rice bowl, low-fat sauce (~150 g) · afternoon — pretzels and a soft drink (~85 g) · dinner — generous pasta, tomato sauce (~105 g) · sweets allowance in between (~65 g). The pattern: white, starchy, low-fat, and let liquids carry a share.
Four ways riders ruin a load
1. Loading the night before: One dinner can't fill a two-day tank — it just fills the stomach.
2. Loading with fat: Carbonara and chips crowd out the carbs and slow the gut. Loading food is plain, starchy, boring — on purpose.
3. Loading with fibre: Wholegrain virtue is for training weeks. For two days, white bread and white rice are the professionals' choice.
4. Fearing the scale: See above — the kilo is water bound to fuel. Racing weight-obsessed and glycogen-full are opposites; pick full.
Who actually needs this (straight answer)
Under ~90 minutes of racing, your everyday tank covers it — a crit or a short Zwift race needs a normal high-carb day, nothing more. From gran fondos and long road races upward, loading buys measurable time. Works the same for women — the early studies just didn't recruit enough of them to say so loudly.
Same-days side quests
The loading window doubles as the beetroot window (over 370 mg of nitrate daily, 2–3 days, last shot ~90 min before the start — the rare supplement where amateurs outgain pros) and as the start of hydration — steady sipping through both days, since the glycogen going in wants its water anyway.
FAQ
How many days should I carb load?
One to two. Longer doesn't add storage — it adds dishes.
How many grams of carbs?
8–10 per kg of body weight per day.
Will I gain weight carb loading?
Yes, on purpose: 1–2 kg of glycogen-bound water that pays itself back mid-race.
Do I need special products?
No. Rice, bread, juice, oats, jam — the supermarket is the supplement.
Loaded — now when does the tank run dry?
In the Fuel Lab your loaded tank becomes a race plan: burn rate, intake, the moment the wall would come — run yours.
All fuel guides →Sources
- Bussau et al. 2002 (one-day loading)
- Jeukendrup (loading protocols)
- Frontiers 2026 meta-analysis (nitrate)
Sources as named — title and year are enough to look them up.
Sport, not medicine: fueling knowledge for healthy athletes, no substitute for medical or dietary advice — and not a weight-loss or weight-gain page: weight appears here only as the water truth. Zwift is a trademark of Zwift, Inc.; this page is an independent project with no affiliation to Zwift. All facts from the sources listed — no AI-generated numbers.