Cycling Nutrition Calculator

Carbohydrate needs are driven by power output, intensity and power output. Your body burns ~1 g of carb per 4 kcal of carb energy used, and the carb fraction of total fuel rises sharply with intensity — from ~20% at easy effort to nearly 100% at race pace:

• 100 W (easy spin): ~30 g/h carb burn
• 150 W (endurance pace): ~70 g/h
• 200 W (tempo): ~120 g/h
• 250 W (threshold): ~190 g/h

The catch: the gut can typically absorb ~60 g/h from a single carb source, or ~90 g/h with a glucose+fructose mix (SGLT1 + GLUT5 dual transporters). Above that ceiling, absorption doesn't improve. For performance: fueling at the maximum tolerable rate is still essential, because at high power your burn rate far exceeds absorption and glycogen is always being drawn down. The deficit can be managed, not eliminated.

Glycogen is the storage form of glucose in muscles and the liver. A typical trained cyclist stores 300–600 g of glycogen (1200–2400 kcal). Muscle glycogen fuels working muscles directly; liver glycogen maintains blood glucose for the brain. At race pace, these stores can be fully depleted in 60–90 minutes without exogenous carbohydrate intake.

If you don't fuel consistently, your glycogen stores deplete and you bonk (hit the wall) — a sudden and severe performance collapse caused by complete glycogen depletion. Unlike normal fatigue, it comes on rapidly: legs stop responding, thinking becomes foggy, and maintaining even an easy pace feels impossible. Without carbohydrate intake, most cyclists reach this point within 90–120 minutes at moderate-to-high intensity. It is entirely preventable by fueling from the start, before hunger sets in.

The right amount depends on power output, not duration. Fat carries most of the load at easy pace (~100–150 W), where carb burn is only 30–70 g/hr. At tempo or threshold (200–250 W), carb burn rises to 120–190 g/hr — well above gut absorption capacity. Individual gut tolerance, heat, and habitual training with carbs all shift the numbers further.

Performance riders should fuel at the gut's ceiling: 60 g/hr from a single carb source, up to 90 g/hr with a glucose+fructose mix (dual SGLT1+GLUT5 transport). Start eating in the first 20–30 minutes — before hunger appears. Casual and recreational riders at lower outputs burn 30–50 g/hr: real food, café stops, and relaxed timing work fine — targeting 90 g/hr at easy pace causes GI distress with no benefit.

Pre-ride nutrition depends on your goal. Performance riders should eat a carbohydrate-rich meal 2–3 hours before to top up glycogen stores — for multi-day events or stage racing, deliberate carb-loading in the days prior is standard practice. Casual and recreational riders have much more flexibility; a light snack beforehand is sufficient.

Whether to fuel during the ride depends on intensity and duration. At high intensity, glycogen depletes fast — start eating within the first 20–30 minutes regardless of pre-ride intake. At easy pace, the urgency is lower and real food with relaxed timing works fine. For any ride beyond 90 minutes at meaningful effort, in-ride fueling is non-negotiable.

There is no single optimal ratio — the right ratio depends entirely on how many grams per hour you are consuming. The intestine has two separate carbohydrate transporters: SGLT1 absorbs glucose (and glucose-releasing sources like maltodextrin), while GLUT5 absorbs fructose. At intakes up to ~60 g/h, glucose alone saturates SGLT1 and no fructose is needed. Above that ceiling, adding fructose opens the second transporter, raising total oxidation rates by up to 50% compared with glucose alone.

• 80 g/h: ~60 g glucose + 20 g fructose (3:1 ratio)
• 90 g/h: ~60 g glucose + 30 g fructose (2:1 ratio) — practical ceiling for most athletes
• 100 g/h: ~60 g glucose + 40 g fructose (3:2 ratio)

The practical rule: keep glucose at 60–70 g/h to saturate SGLT1, then add fructose to reach your carb target. Gut adaptation through consistent high-carb training is required to tolerate intakes above 90 g/h.

The three modes take their names from a viral Brazilian cycling meme that ranks athletes, gear and approaches on a three-tier scale: Peba (basic/budget), Bruto (raw and powerful), and Galático (elite, otherworldly).

🐢 Peba — designed for casual riders who fuel with whatever is at the aid station: Gatorade, banana, Coca-Cola, paçoca. Duration is capped at 6 hours and carbs at 60 g/h (the single-transporter limit).

🐴 Bruto — for athletes who train with gels and packaged sports nutrition. Extends duration to 16 hours and carbs to 120 g/h (dual-transporter glucose + fructose).

👽 Galático — the max-performance tier. Takes your FTP and target % FTP as inputs, adds a glycogen depletion chart, and builds a precision plan using maltodextrin and fructose dissolved directly in your bottles.