Estimate how much carbohydrate your chosen hourly fuelling target adds up to over a long run. Practise your plan in training.
Race-day fuelling calculator
Estimate carbohydrate needs and a practical reminder schedule for long races. Practise with familiar products in training; tolerance varies and this is not individual medical advice.
Why this calculator is useful
Estimate total carbohydrate from session duration and an hourly target, then plan how to practise intake in training.
How to use it
- Enter a recent, representative result or your planned race details, using the units shown beside each field.
- Select Calculate and review the result, including the assumptions and limitations shown.
- Use the result as a planning aid, compare it with how you feel, and recalculate when your inputs change.
Results are estimates, not guarantees. Fitness, recovery, weather, terrain, elevation and course conditions can all change the outcome.
Related running resources
All running calculators · Running guides · Training plans · UK race calendar · Triathlon and Ironman guide
Frequently asked questions
What does the fuelling planner calculate?
It multiplies your chosen carbohydrate target per hour by the planned session duration to estimate a total in grams.
How much carbohydrate should I take?
Needs vary with duration, intensity, body size, tolerance and prior practice. Start conservatively and build tolerance gradually; seek qualified advice if you have medical or dietary concerns.
Should I test my race fuelling before event day?
Yes. Practise the products, timing and fluids you plan to use during training rather than trying something new on race day.