How to use
- Enter the inputs.
- Sanity-check the outputs.
- Use the result as a planning anchor, not a promise.
Jump to
Tool
Inputs → outputs
This page is intentionally practical: get numbers first, then read the how-to.
Inputs
- • Known distance (5K/10K/HM/Marathon)
- • Known time (hh:mm:ss)
- • Fatigue factor (exponent) (optional)
Outputs
- • Predicted times table
- • Predicted paces (per km/mile)
Export
Print or share the tool
Useful outputs beat generic SEO copy. Print a PDF or share this page before race week.
Tip: print or save as PDF for race week.
Example presets
Prefill with a realistic scenario
Pick an example to prefill the calculator, then tweak inputs for your own training week.
Loading race time predictor…
Quick answers
The 60-second version
Snippet-ready answers to common questions. Use the calculator above for the numbers.
What is the fatigue factor (exponent)?
It controls how much the model expects you to slow as distance increases. Higher values predict more slowdown; the default is a common baseline.
Is this accurate for first-time marathoners?
Treat it as a rough estimate. First marathons are often limited by durability and fueling, not raw speed — execute a plan and practice fueling.
How should I use this for pacing?
Use it to set a realistic goal range, then pace by effort on race day and adjust for heat/hills. Don’t chase perfect splits in bad conditions.
Assumptions
What this tool assumes
- • Your known result reflects current fitness (recent and executed well).
- • Conditions and course difficulty are broadly comparable across distances.
Limitations
What can break it
- • Longer races require durability + fueling; many runners slow more than the model predicts without specific training.
- • Does not adjust for heat, hills, wind, altitude, or course difficulty.
Related
Use this with a plan
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FAQs
What is the fatigue factor (exponent)?
It controls how much the model expects you to slow as distance increases. Higher values predict more slowdown; the default is a common baseline.
Is this accurate for first-time marathoners?
Treat it as a rough estimate. First marathons are often limited by durability and fueling, not raw speed — execute a plan and practice fueling.
How should I use this for pacing?
Use it to set a realistic goal range, then pace by effort on race day and adjust for heat/hills. Don’t chase perfect splits in bad conditions.
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