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 |