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Ironman 70.3 fueling planner

Compute totals for carbs, sodium, and fluids from your bike/run durations and hourly targets — then practice in training.

Updated Jul 26, 2026

Use the tool
On this page

Your path

Perform on the day

The decision this page helps you make

Make the carbohydrate, sodium, and fluid assumptions explicit, then test them during suitable bike and run sessions.

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Example presets

Prefill with a realistic scenario

Pick an example to prefill the calculator, then tweak inputs for your own training week.

Tool

What you enter and what you get

Enter a few details to get your result. The guide below explains how to use it.

You enter

  • Bike duration (hh:mm)
  • Run duration (hh:mm)
  • Carbs bike (g/h)
  • Carbs run (g/h)
  • Sodium bike (mg/h) (optional)
  • Sodium run (mg/h) (optional)
  • Fluid bike (ml/h) (optional)
  • Fluid run (ml/h) (optional)

You get

  • Total carbs (g)
  • Total sodium (mg)
  • Total fluid (ml)

Use the totals to plan a rehearsal

This planner converts bike and run duration plus hourly assumptions into carbohydrate, sodium and fluid totals. It cannot determine what your gut, sweat rate, medical history or race conditions make appropriate. Treat every output as a hypothesis to rehearse.

Start with the products and amounts already tolerated during long rides and bricks. Record the actual label values; a "gel" is not a standard unit, and drink concentration changes when bottle size or powder scoops change.

Build a bike-to-run worksheet

SegmentPlanned timeProductCarbohydrateFluidSodiumCarry or collect
Bike hour 1__________________
Bike hour 2__________________
Final bike section__________________
Run opening__________________
Run remainder__________________

Keep bike and run assumptions separate. An intake tolerated while cycling may be difficult at running intensity, and a late bike surge can change the run response even when the arithmetic is unchanged.

Rehearse one change at a time

Use a long ride plus short brick workout:

  1. copy the planned timing into a watch or bottle checklist;
  2. use the same position, products and concentration expected on race day;
  3. record missed intake, thirst, hunger, bloating, nausea and bathroom stops;
  4. keep effort controlled enough to evaluate the plan;
  5. change only one major variable before repeating.

Sports-nutrition position statements provide population ranges, not a personal prescription. Environmental heat, sweat rate, body size, intensity, product tolerance and medical conditions all change the decision.

Check event logistics

Confirm the current athlete guide: bottle rules, on-course products, aid-station locations, special-needs access and litter zones. Do not assume that last year's sponsor or layout still applies. Build a fallback for one dropped bottle or missed station without doubling the next intake.

Use the IRONMAN 70.3 training hub to place rehearsals in the build. Race week is for confirming a tested plan, not introducing a new concentration.

Stop rules

Repeated vomiting, confusion, fainting, severe breathing difficulty, chest pain or inability to keep fluid down requires event medical support. More fluid is not automatically safer; exercise-associated hyponatremia is a serious risk. This planner is educational and not medical advice.

Assumptions

What this tool assumes

  • Hourly targets are based on what you tolerate in training (not a prescription).
  • Bike fueling is typically easier than run fueling — don’t assume equal tolerance.

Limitations

When this estimate may be less reliable

  • Does not replace professional nutrition guidance for medical conditions.
  • Heat and sweat rate can change fluid/sodium needs dramatically.

Adaptive AI coach for iPhone

Meet your adaptive AI coach.

Tell your coach what you are training for. It builds the plan, follows the work you complete, and adapts upcoming training when recovery, your schedule, or real life changes.

FAQs

Should bike and run fueling targets be the same in a 70.3?

Not automatically. Use separate, rehearsed assumptions because posture, intensity and gastrointestinal tolerance can change between cycling and running.

How do I choose a carbohydrate target?

Use sports-nutrition guidance as a range, then begin with an amount already tolerated and test the exact products and timing in long rides and bricks.

Does the planner account for on-course aid stations?

No. Confirm the current event guide, then map what you carry and collect. Product brand, concentration and station layout are event-specific.

What should I do after a missed bottle or gel?

Use a rehearsed fallback and avoid automatically doubling the next intake. Adjust to the remaining course, symptoms and available aid.

Keep going

Sources