Race Fueling Calculator

Plan your carbs, gels, fluid, and sodium for race day. Based on the Jeukendrup / ISSN guidance every sports nutritionist uses.

Race distance

Expected finish time Format: h:mm:ss or mm:ss.

Body weight

Unit

Conditions

Gel

Practice your race-day fuelling in long runs — the gut adapts to higher carb intakes only if you train it. Tolerance for the upper end of these ranges (90–120 g/hr) varies a lot between athletes. If you cramp, drop sodium first; if you bonk, raise carbs.

Race fuelling on paper. Empace helps you actually pull it off.

Empace can help you create personalised tips to improve your fuelling — building long runs that rehearse race-day intake, then locking in your gel, fluid, and sodium plan in a race-week briefing so nothing is experimental on the start line.

Fuelling rehearsals baked into your long-run progressions.
Race-week briefing with your full intake plan locked in.
Gut-training progressions to push you toward 90 g/hr safely.

★★★★★“Surprised how nice it was to chat with it. Got a few good suggestions for how to train with my injury.” — Robert Wrehammar, ultra marathoner

How this is calculated

Carbs per hour follow the Jeukendrup / ISSN bands by duration: under 60 min, 0–30 g/hr (often optional); 60–150 min, 30–60 g/hr; 150 min and longer, 60–90 g/hr. Highly trained guts can push to 90–120 g/hr with multiple-transportable carb mixes. We nudge the midpoint with conditions — cool weather tolerates the upper end of the band; heat impairs gut absorption, so the target trends lower.

Fluid ranges scale by conditions and body weight: cool 400–600 mL/hr, warm 500–750 mL/hr, hot 600–900 mL/hr. Sodium scales with sweat losses — ~400 mg/L (cool), ~500 mg/L (warm), ~700 mg/L (hot). Salty sweaters may need more.

Pre-race meal is 2 g/kg body weight in carbs, 2–3 hours before. For races over 90 minutes, carb-load 8–10 g/kg/day for 24–36 hours leading in.