Every runner knows the feeling: you’ve trained for months, dialed in your pacing, visualized the course… and then race day arrives, and the one thing that can make or break the entire effort is the part most runners still guess at — fueling.
Carbs, electrolytes, timing, temperature, bodyweight, race duration — they all matter. But until now, putting them together into a simple, personalized plan has been harder than it should be.
That’s why I built the Run with Didier – Race Fueling Calculator.
This tool takes the science of endurance fueling and turns it into a clean, practical plan you can use immediately — whether you’re racing a 5K, half marathon, marathon, or anything in between.
Why Fueling Matters More Than You Think
Most runners underfuel. Not because they don’t care — but because the numbers feel abstract:
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How many carbs per hour do you need
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How does temperature change your hydration needs
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What’s the right balance of electrolytes
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How do you carb‑load without overdoing it
The calculator answers all of that in seconds.
What the Calculator Actually Does
When you enter your details — bodyweight, age, race distance, expected duration, and race‑day temperature — the tool generates:
1. Your Carb‑Loading Plan (2–3 days before the race)
Based on your race duration, the calculator gives you a tailored carb‑loading target so you start race day with full glycogen stores.
2. Your Hour‑by‑Hour Race Fueling Strategy
You’ll get a clean breakdown of:
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Carbs per hour
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Total carbs for the race
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Gel count (or equivalent fuel)
3. Your Electrolyte & Hydration Needs
Temperature matters — a lot. The calculator adjusts your hydration and electrolyte targets based on whether your race is cool, mild, warm, or hot.
4. A Clean, Email‑Ready Plan — With a Little Something Extra
When you email the plan to yourself, you’ll also receive one more thing: a small Activastic training perk to help you fuel and recover well in the weeks ahead. Nothing flashy — just something useful.
Why I Built This Tool
I’ve been running long enough to see it happen again and again: we train hard, feel ready, and still fall apart at mile 18 or mile 9 or even mile 3 when our fueling isn’t in line with what our body or the day actually demands.
I wanted to remove that barrier.
I wanted something simple, accurate, and runner‑friendly — a tool that reflects the way we actually race, not the way textbooks assume we do.
Ready to Build Your Race‑Day Fueling Plan?
Use the Race Fueling Calculator to get your personalized carb, hydration, and electrolyte strategy — plus a small training perk waiting in your inbox.
Tap the visual below to open the calculator.
How to Use It
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Open the Race Fueling Calculator
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Enter your race details
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Review your personalized plan
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Email it to yourself
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Practice it on your long runs
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Show up on race day with confidence
Fueling shouldn’t be complicated. It should be automatic, and whether you’re gearing up for your first half marathon or chasing a marathon PR, this tool will help you fuel smarter, run stronger, and finish proud of the work you put in.
Your training deserves that.