How Kaliber calculates

Last updated: June 28, 2026

Kaliber turns your race, your body, and your sweat rate into three per-hour numbers — carbs, fluid, and sodium — plus a packing list and a timed schedule. Every number is a starting default drawn from published sport-science ranges, and every number is yours to adjust. Here is where each one comes from.

Carbohydrate — 30 to 120 g per hour

How much carbohydrate you can use is limited by your gut, not your bodyweight, so Kaliber plans it in absolute grams per hour — the way the research expresses it. A single carbohydrate type (glucose or maltodextrin) saturates its intestinal transporter at roughly 60 g/hr. Going higher needs a glucose-and-fructose mix (around 2:1), which recruits a second transport pathway and lets a trained gut reach about 90 g/hr. Longer races sit higher in the range; very short ones need little or none.

Basis: Jeukendrup, carbohydrate-during-exercise reviews; ACSM / Academy of Nutrition and Dietetics / Dietitians of Canada 2016 joint position stand, "Nutrition and Athletic Performance."

Fluid — 400 to 800 ml per hour

Fluid is matched to how much you sweat, not a fixed "drink more" figure. Kaliber keeps the default inside a practical band: too little invites dehydration, while past roughly 800 ml/hr the stomach struggles to empty fast enough and steadily drinking more than you sweat out can dilute your blood sodium (a condition called hyponatremia). In the hours before the start, a separate preload of about 5–7 ml per kilogram of bodyweight is the common guidance.

Basis: American College of Sports Medicine fluid-replacement guidance; international exercise-associated hyponatremia (EAH) consensus statements.

Sodium — 300 to 1500 mg per hour

Sodium replaces what you lose in sweat, so Kaliber multiplies your sweat rate by your sweat's sodium concentration rather than guessing from bodyweight. Sweat sodium varies roughly tenfold between people — about 460 to 1,840 mg per litre — which is why a generic number misses the mark, and why Kaliber asks for yours. Taking in more sodium than you lose does not improve performance and does not let you safely drink more.

Basis: international exercise-associated hyponatremia (EAH) consensus statements; published sweat-sodium ranges.

These are defaults, not prescriptions

Kaliber gives general fueling guidance, not medical advice, and it is not a substitute for professional judgment. Bodies and conditions differ. Train with your plan before race day, and talk to a doctor or a sports dietitian before making decisions about your nutrition, hydration, or health — especially if you have a medical condition.

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