Calculator Inputs
Use one method or both. Hybrid mode combines pace planning with recent race evidence for a more realistic marathon prediction.
Example Data Table
| Scenario | Target Pace | Weather Adj. | Aid Delay | Projected Finish |
|---|---|---|---|---|
| Steady cool-day effort | 5:00 / km | 0.0% | 0 sec | 03:30:58 |
| Moderate fatigue race | 5:30 / km | 1.5% | 90 sec | 03:57:03 |
| Hot course management | 6:00 / km | 3.0% | 120 sec | 04:22:46 |
Formula Used
This calculator uses a layered marathon projection model instead of a single rough estimate.
1) Direct pace projection
Base Time = Target Pace × Marathon Distance
Marathon distance is 42.195 km or 26.218757 mi.
2) Race-based Riegel projection
T2 = T1 × (D2 ÷ D1)Exponent
T1 is your recent race time, D1 is your recent race distance, and D2 is marathon distance.
3) Hybrid projection
Hybrid Base = (Direct Projection × 0.50) + (Riegel Projection × 0.50)
4) Condition adjustments
Adjusted Finish = Base + Weather + Elevation + Aid Delay + Safety Buffer
Weather and safety buffer are percentage-based. Elevation penalty is seconds per 100 meters climbed.
5) Split distribution
First Half = Adjusted Finish ÷ (1 + Second-Half Factor)
Second Half = Adjusted Finish − First Half
A positive second-half factor simulates slowdown. A negative value simulates a faster close.
How to Use This Calculator
- Select your preferred calculation method.
- Enter a target pace, recent race data, or both.
- Choose a realistic second-half pace change percentage.
- Add weather, elevation, aid-station delay, and safety buffer assumptions.
- Press the calculate button to show results above the form.
- Review finish time, average pace, split table, and chart.
- Use the export buttons to save your results as CSV or PDF.
FAQs
1) Is this marathon finish time exact?
No. It is a planning estimate built from pace, recent race evidence, and race-day assumptions. Your actual result can change with training, weather, nutrition, and pacing discipline.
2) Which method should I choose?
Use direct pace when you already know your sustainable marathon pace. Use the Riegel method when you trust a recent race result. Use hybrid mode when you want a balanced prediction.
3) What does second-half pace change mean?
It models how your pace shifts after halfway. Positive percentages mean a slower closing half. Negative percentages mean you expect a stronger finish and a mild negative split.
4) How should I enter weather adjustment?
Use a positive percentage for heat, humidity, wind, or poor conditions. Use a negative value only when you expect clearly favorable conditions and good race-day support.
5) Why include elevation gain?
Climbing usually costs time, especially late in the race. The calculator converts elevation gain into extra seconds so the result better reflects a harder course profile.
6) Can beginners use this calculator?
Yes. Beginners can start with target pace only. More experienced runners can improve the forecast by adding recent race data, pacing drift, elevation, and delay assumptions.
7) What do the CSV and PDF exports include?
The exports include your summary metrics and split table. They are useful for race planning, sharing with a coach, or saving a pacing plan before race day.
8) Does the calculator support kilometer and mile pacing?
Yes. You can enter target pace in either kilometers or miles. The results also show average pace in both units for easier comparison and training use.