Ironman Pace Calculator

Plan your perfect Ironman triathlon with pacing strategies for all three disciplines and transitions.

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Ironman Pacing Principles

Successful Ironman pacing requires discipline-specific strategies that account for energy conservation and nutrition:

  • Swim: Start conservatively to avoid early fatigue
  • Bike: Maintain steady power output (70-75% FTP)
  • Run: Negative split the marathon when possible
  • Transitions: Practice efficiency but don't rush

Ironman Time Distribution

Typical time allocation by discipline for a 12-hour Ironman:

Discipline Time % of Total Pace/Power
Swim 1:10-1:30 10-12% 1:50-2:00/100m
T1 5-10 min 1% N/A
Bike 6:00-6:30 50-54% 70-75% FTP
T2 5-10 min 1% N/A
Run 4:00-4:30 33-38% 30-45 sec/mi slower than marathon pace

Bike Power Zones for Ironman

Optimal power output ranges based on goal time:

Goal Time % of FTP NP Range VI Target HR Zone
Sub-9hr 75-78% 0.75-0.80 IF <1.05 Z2-Z3
9-11hr 72-75% 0.72-0.75 IF <1.07 Z2
11-13hr 68-72% 0.68-0.72 IF <1.10 Z1-Z2
13+hr 65-68% 0.65-0.68 IF <1.12 Z1

Run Pace Strategy

Marathon pace relative to standalone marathon time:

Experience Level Pace Adjustment First Half Second Half Walk Strategy
First Ironman +45-60 sec/mi Easy conversational Maintain if possible 1 min walk per aid station
Intermediate +30-45 sec/mi Moderate effort Small negative split 30 sec walk every 2 miles
Advanced +15-30 sec/mi Controlled pace Negative split Minimal walking

Nutrition Planning

Ironman calorie and fluid intake guidelines:

Time Calories/hr Carbs/hr Fluid/hr Sodium/hr
Swim N/A N/A Pre-hydrate Pre-load
Bike 300-400 60-90g 20-30oz 500-700mg
Run 200-300 30-60g 15-25oz 400-600mg

Frequently Asked Questions

How do I pace my first Ironman?

Recommended pacing strategy for first-time Ironman athletes:

Discipline Pacing Approach Key Focus
Swim Start at back/side, steady effort Avoid overexertion
Bike 70% FTP, even power Nutrition execution
Run Conversational pace first 10K Manage energy

What's a good bike-run pace relationship?

Optimal bike/run pacing ratios by goal time:

Goal Time Bike % of FTP Run Pace vs MP Bike:Run Time Ratio
Sub-9hr 75-78% +15-25 sec/mi 1.5:1
9-11hr 72-75% +25-35 sec/mi 1.6:1
11-13hr 68-72% +35-45 sec/mi 1.7:1
13+hr 65-68% +45-60 sec/mi 1.8:1

How should I adjust for hilly courses?

Course-specific pacing adjustments:

Course Type Bike Strategy Run Strategy Gear Selection
Flat/Fast Steady power Even pacing Big chainring focus
Rolling 5% power variation Effort-based pacing Frequent shifting
Hilly 10% power variation Walk steep hills Compact crankset

What nutrition mistakes should I avoid?

Common Ironman nutrition errors:

Mistake Consequence Solution
Starting nutrition too late Early bonking Begin fueling in first 30 min
Over-concentrated drinks GI distress Test concentration in training
Changing products race day Unexpected reactions Use only tested products
Neglecting sodium Hyponatremia 500-700mg sodium/hour