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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.

Last updated/Feb 03, 2026, 02:17 PM

Tool

Inputs → outputs

This page is intentionally practical: get numbers first, then read the how-to.

Inputs

  • • 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)

Outputs

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

Examples

Bike 2:45, run 1:50
Totals reflect segment durations; practice on bricks so your gut is trained, not surprised.
Bike 3:15, run 2:05
Slower durations increase totals; adjust for heat and aid-station realities.

Planner

70.3 fueling totals (bike + run)

Estimate totals based on segment durations and hourly targets. Practice in training and adjust to your gut and heat conditions.

Durations

Hourly targets

Total carbs

330 g

Total sodium

2842 mg

Total fluid

2842 ml

Safety note: hydration and sodium needs vary widely. Heat, sweat rate, and GI tolerance matter. Practice and consult a professional if you have medical concerns.

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

What can break it

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

Related

Use this with a plan

24-week 70.3 plan
Open plan
70.3 training hub
Open plan
Marathon race directory (example athlete guides)
Open race guide
Berlin Marathon athlete guide (example)
Open race guide
Taper week checklist
Open guide

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FAQs

Should I fuel the same on bike and run?

Usually no. The run is higher impact and many athletes tolerate less. Practice bricks to find your run target.

How early should I start fueling?

Start early on the bike, then keep it steady. On the run, use a simpler, tolerable schedule.

Do I need to drink to thirst?

Thirst is useful but not perfect in heat. Practice a plan and adjust to conditions; avoid extremes.

Keep going

24-Week Ironman 70.3 Training Plan

A 24-week 70.3 training plan with week-by-week structure, bricks, adaptation rules, and built-in fueling tools. Variations are included on one page.

Ironman 70.3 Training Hub

70.3 training plans, fueling tools, and execution checklists — focused on pacing and repeatable weeks.

Marathon Races (Directory + Athlete Guides)

Curated marathon race directory with athlete guides. Facts include sources, verification timestamps, and planning tools.

BMW Berlin Marathon 2026: date, registration, course, weather

Athlete guide for BMW Berlin Marathon 2026: date, location, climate context, training timeline, and pacing/fueling tools.

Taper Week Checklist (Arrive Fresh, Not Flat)

A practical taper checklist: what to reduce, what to keep, and what to rehearse so race week is calm and repeatable.

Sources