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🏃 Your Performance
: :
🌡 Race Conditions
12°C
Cold Optimal Hot
📈 Pacing Strategy
Projected Finish Time
--:--:--
Pace: --:-- /km Score: -- VDOT
Riegel (Optimistic) --:--:--
Cameron (Realistic) --:--:--
Weather Penalty 0%
Glycogen Limit ~32 km
Race Plan (Even)
Km Split Elapsed
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About

Professional marathon prediction extends beyond simple multiplication. It involves analyzing physiological decay curves, metabolic thresholds, and environmental resistance. This tool is not a simple linear calculator; it is a performance architect designed for serious runners.

We utilize a weighted hybrid of the Riegel Fatigue Formula and the Cameron Model. While Riegel excels at projecting performance between similar distances (e.g., 10K to Half Marathon), Cameron provides superior accuracy when extrapolating from shorter anaerobic efforts to aerobic endurance events. Furthermore, we account for Cardiac Drift caused by thermodynamics. Running in 20°C heat requires significantly more oxygen for thermoregulation than running in 8°C, directly impacting your potential finish time.

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Formulas

The core prediction logic utilizes the Riegel Power Law, modified for environmental variables.

T2 = T1 × (D2D1)k × Wfactor

Where k is the fatigue coefficient (standard 1.06, conservative 1.08). The Weather Factor (Wfactor) is calculated using a non-linear decay curve based on the Wet Bulb Globe Temperature estimate:

Wfactor = 1 + max(0, (Tcurr Topt)1.5 × 0.0015)

Reference Data

Distance CategoryStandard NameTime (h:m:s)Pace (min/km)Context
MarathonMen's World Record2:00:352:51Kelvin Kiptum (2023)
MarathonWomen's World Record2:11:533:07Tigst Assefa (2023)
MarathonBoston Q (Men 18-34)3:00:004:16Requires ~1:26 Half
MarathonBoston Q (Women 18-34)3:30:004:58Requires ~1:40 Half
Half MarathonSub-90 Barrier1:29:594:15Key amateur milestone
Half MarathonSub-2 Barrier1:59:595:41Average recreational pace
10KSub-40 Barrier0:39:594:00High-performance amateur
5KSub-20 Barrier0:19:594:00Gateway to serious training

Frequently Asked Questions

Riegel's formula (D2/D1)^1.06 is the industry standard but tends to be optimistic for recreational runners moving from 5K to Marathon. The Cameron model accounts for the non-linear decline in VO2 Max efficiency over longer durations. Our tool uses a weighted average (Hybrid) to provide the most realistic "Safe Start" pace.
A Negative Split means running the second half of the race faster than the first. Historical data from World Majors shows that 95% of world records are set with a negative split. It conserves glycogen stores in the first 20 miles, preventing the dreaded "Wall" at mile 22.
Mathematical formulas assume proper training and fueling. If you input a 10K time but haven't done the long runs (30km+), the prediction will be inaccurate. The "Conservative" estimate in this tool adds a 2% buffer to account for potential endurance deficits.
The tool checks against the official 2025 qualifying standards. However, meeting the standard does not guarantee entry; widely popular races often have a "cutoff" time (e.g., BQ-5 minutes) that varies yearly. Aim for 5 minutes faster than the standard shown.