Pace Calculator
Marathon Pace Calculator
Marathon pacing can make or break your race. Starting too fast almost always leads to "hitting the wall" after 30km. Use our calculator to plan realistic splits and develop a race-day strategy based on your training.
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Use our pace calculator with these considerations in mind.
Key Considerations
- Start your marathon 10-15 seconds per km slower than target pace for the first 5km
- Negative splits (second half faster than first) are the most reliable strategy
- Most marathon runners slow down 10-20% in the final 10km
- Your marathon pace should be 60-90 seconds per km slower than your 5K pace
- Weather conditions (heat, wind, rain) significantly affect achievable pace
Specific Adjustments
First Marathon
Be conservative. Aim for even splits and focus on finishing strong rather than a specific time. Run 15-20 seconds per km slower than your "dream" pace.
Experienced Runner
Negative split strategy: first half at target pace, second half 5-10 seconds per km faster. This requires discipline in the early miles when you feel fresh.
Tips for Best Results
1Practice your target pace during long training runs (at least 3 runs at marathon pace)
2Fuel every 30-45 minutes with gels, starting from the first aid station
3Hydrate before you feel thirsty — losing 2% bodyweight in sweat impairs performance
4Do not chase other runners in the first half — run your own race
5Wear the same shoes, clothing, and nutrition you used in training — nothing new on race day
Frequently Asked Questions
How do I predict my marathon pace?
The most reliable predictor is your recent half marathon time multiplied by 2.1-2.2. For example, a 1:45 half marathon suggests a 3:40-3:51 marathon. Training volume and long run quality also factor in.
What happens if I start too fast?
Starting too fast depletes glycogen stores prematurely, leading to "the wall" around 30-35km. Your pace can slow dramatically (2-5 min/km) and the last 10km becomes a survival march.
Should I run negative splits?
Yes, for most runners. Running the second half slightly faster than the first is the most reliable strategy. It requires patience in the early kilometres when you feel strong.
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