Marathon Time Predictor

26.2 mi via Riegel. Most accurate from a recent half marathon.

Inputs

Result

Loading calculator…
—

How to use this calculator

  • Enter recent race time.
  • Read marathon prediction.

About this calculator

Marathon predictor: 26.2 mile race time from recent shorter race. Most accurate from a recent half-marathon — same race-day fitness. From 5K, prediction is optimistic — extrapolation too far ignores marathon-specific endurance. Add 5-10% buffer if your longest training run is below 18 miles. World marathon record: 2:00:35 (Kelvin Kiptum, 2023).

Frequently asked

Best base?+
Half-marathon within 6 weeks. Closest physiology to marathon.
Why so much error from 5K?+
5K is glycolytic + VO2 max. Marathon is fat oxidation + glycogen storage + mental endurance. Different systems.
BQ (Boston qualifying) times?+
Vary by age + sex. Male 18-34: 3:00:00. Female 18-34: 3:30:00. Adjusted by 5-min/decade.
Wall avoidance?+
Long runs (18-22 mi) train fat oxidation. Carb-load 24-48hr pre-race. In-race fueling 30-60g carbs/hr.
Negative split?+
Faster second half. Most successful marathons negative or even split. Positive splits = went out too fast.

Related calculators

5K Time Predictor (Riegel)
Predict 5K from another race using Riegel formula: T₂ = T₁ × (D₂/D₁)^1.06.
10K Time Predictor (Riegel)
Predict 10K via Riegel: T₂ = T₁ × (D₂/D₁)^1.06.
Half Marathon Time Predictor
Predict 13.1 mi via Riegel.
Race Time Predictor (Riegel formula)
Predict your time at any distance using Riegel's formula T₂ = T₁ × (D₂/D₁)^1.06.
VO2 Max from Cooper 12-Min Run
VO2max ≈ (distance in meters − 504.9) / 44.73. Cooper test estimates aerobic fitness.
Lactate Threshold Pace Estimator
LT pace ≈ pace you can hold for 60 min. Estimate from recent race or HR zone.

More tools you might like

Hand-picked tools that pair well with this one — same audience, same intent.

Half Marathon Time Predictor
Calc

Predict 13.1 mi via Riegel.

10K Time Predictor (Riegel)
Calc

Predict 10K via Riegel: T₂ = T₁ × (D₂/D₁)^1.06.

Race Time Predictor (Riegel formula)
Calc

Predict your time at any distance using Riegel's formula T₂ = T₁ × (D₂/D₁)^1.06.

5K Time Predictor (Riegel)
Calc

Predict 5K from another race using Riegel formula: T₂ = T₁ × (D₂/D₁)^1.06.

Lactate Threshold Pace Estimator
Calc

LT pace ≈ pace you can hold for 60 min. Estimate from recent race or HR zone.

Running Pace Calculator
Health

Pace, speed, and a full per-km and per-mile splits table for 5K / 10K / Half / Marathon at your entered pace. Toggle between km and miles for the input.