Marathon Pace Predictor

Predicted Marathon Pace

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Runs/wk {{ weeklyRuns }} {{ weeklyDistanceBadge }} {{ trainingSpeedBadge }} {{ efficiencyRatioDisplay }}

Weekly distance:

Enter 5-250 in km/week or mi/week, e.g. 80 km/week.

Average training speed:

Use moving speed from aerobic runs, e.g. 10.5 km/h or 6.5 mph.

Runs per week:

Enter whole sessions from 1-14, including long runs and workouts.

sessions

Model adjustment: {{ tanda_adjustment_percent > 0 ? '+' : '' }}{{ tanda_adjustment_percent.toFixed(1) }}%

Range -12% to +12%; positive slows the predicted finish, negative speeds it up.

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Metric	Value	Copy
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Keep in mind {{ index + 1 }}

Marker	Distance	Cumulative time	Segment pace	Copy
{{ split.label }}	{{ split.distanceDisplay }}	{{ split.timeDisplay }}	{{ split.paceDisplay }}

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Marathon pace prediction turns recent training into a race-day estimate for 42.195 kilometers. The result is useful when a goal time sounds attractive but needs to be checked against weekly distance, ordinary training speed, and how often the runner actually trains.

A training-based marathon estimate is not a race guarantee. It cannot know the course profile, heat, wind, fueling, taper quality, injury risk, or whether the runner will pace the first half sensibly. Its value is in making a goal concrete enough to test: finish time, average pace, checkpoint splits, and the training profile behind the number.

Marathon training inputs flowing into finish time, pace, and checkpoint splits

The strongest input set comes from a stable recent block, not a peak week or a single fast workout. Weekly distance, average training speed, and run frequency should describe the same period. Mixing a high-mileage month with a faster later workout can make the estimate look more precise than the training record supports.

The best use is conservative goal setting. If the predicted pace is faster than recent long runs and marathon-specific workouts can support, the split table should be treated as a warning rather than a target.

How to Use This Tool:

Enter one consistent training block, review the baseline, then use warnings and splits to decide whether the race pace deserves trust.

Enter Weekly distance from a recent steady block. Use kilometers or miles to match your training log.
Enter Average training speed from ordinary aerobic runs, not from intervals or race-pace sections alone.
Set Runs per week to the number of sessions from the same block, including long runs and workouts.
Leave Model adjustment at 0% for the first pass. Use it only when prior marathons show that this model is consistently fast or slow for you.
Read Finish time, average pace, average speed, and Race vs training speed together. A single attractive finish time is not enough.
Check warnings before using the split table. A low-mileage, out-of-speed-range, elite-level, or very slow estimate needs extra caution.
Use the checkpoint splits and charts as planning aids after the top-line result passes a sanity check against recent training.

Interpreting Results:

The finish time is the anchor result, but the warning badges decide how much confidence it deserves. A prediction with no warnings and a familiar race-versus-training speed ratio is easier to use than a faster result that sits outside the model's main training ranges.

Checkpoint splits assume even effort from start to finish. They are practical for watch plans, pacing bands, or a race card, but they do not account for hills, hot weather, crowding, aid-station walking, or late fatigue. If your marathon plan includes a deliberate slow start or negative split, adapt the cumulative times rather than following every marker literally.

How to interpret marathon pace prediction outputs
Output	What it means	What to check
`Finish time`	Adjusted marathon estimate for 42.195 km.	Compare with recent marathon-pace workouts and long-run durability.
`Average pace`	Constant pace needed to hit the finish estimate.	Make sure the pace is sustainable, not just mathematically possible.
`Race vs training speed`	Predicted race speed divided by average training speed.	Large gaps deserve caution unless your workouts support them.
`Sub-4h boundary`	Training speed required for a 240-minute marathon at the selected run frequency.	Use it as a training profile comparison, not as a promise.

The adjustment slider changes every derived result together. A positive adjustment slows the finish and all splits; a negative adjustment speeds them up. Use small changes when you have evidence from past races, not to force a preferred goal.

Technical Details:

The Tanda-style training equation links marathon time to three training indices: weekly distance, average training speed, and runs per week. All three inputs must describe the same training period because the coefficients assume they work together. A runner with fast steady runs but little weekly volume can still receive a caution because marathon performance depends heavily on durability across the full distance.

The marathon distance is fixed at 42.195 km. Distance entered in miles is converted to kilometers, and speed entered in mph is converted to km/h before the equation is applied. The adjusted finish time then drives pace, speed, checkpoint splits, and the training-readiness chart.

Formula Core

t_{base} = 326.3 + 2.394 T - 12.06 V - 46.1 R

t_{adj} = t_{base} \times (1 + \frac{p}{100})

{pace}_{km} = \frac{t_{adj} \times 60}{42.195}

In the formula, T is weekly distance in km/week, V is average training speed in km/h, R is runs per week, p is the adjustment percentage, tbase is baseline time in minutes, and tadj is adjusted time in minutes. The pace equation returns seconds per kilometer; mile pace uses the same adjusted time with 26.2188 miles.

For example, T = 40, V = 8, and R = 2 gives tbase = 326.3 + 2.394 x 40 - 12.06 x 8 - 46.1 x 2, or about 233.4 minutes before adjustment. With p = 0, the adjusted finish remains about 3:53:24.

Marathon model warning thresholds
Check	Threshold	Meaning
Low weekly distance	`T < 40` km/week	Very low mileage can make the estimate too optimistic.
High weekly distance	`T > 180` km/week	The training volume is beyond the original study coverage.
Training speed range	`V < 8` or `V > 15` km/h	The speed is outside the main calibration band.
Elite-level output	`tbase < 140` minutes	Only elite-ready data supports this range cleanly.
Very slow output	`tbase > 330` minutes	The model was built mostly around faster marathon performances.

The split table divides the adjusted marathon time proportionally across fixed markers at 5 km, 10 km, 15 km, halfway, 25 km, 30 km, 35 km, 40 km, and the finish. Segment pace is calculated from the distance between adjacent markers, so each row remains an even-effort projection rather than a separate fatigue estimate.

The sub-four-hour readiness line solves the same equation for the training speed needed to make tbase = 240 minutes at the selected run frequency. It is a model boundary for comparing training distance and speed, not an independent validation of race readiness.

Worked Examples:

Checking a first marathon goal. A runner averaging 55 km per week, 9.5 km/h on steady runs, and four runs per week should read the finish estimate with the warnings visible. If the pace is faster than recent long-run efforts, the safer plan is to choose a slower target and use the split table for conservative checkpoints.

Using a model adjustment. A runner with several past marathons sees that the baseline estimate is usually about five minutes too fast. A small positive Model adjustment slows the finish and every split together. That is a valid calibration because it comes from repeated race evidence.

Reading the sub-four-hour chart. A current profile below the 240-minute boundary means the selected weekly distance and training speed do not line up with a sub-four estimate at the chosen run frequency. It does not mean the runner cannot improve, and it does not replace a race-specific training plan.

Handling warnings. If the average speed is outside 8 to 15 km/h or weekly distance is below 40 km, keep the result as a rough planning number. The calculated finish may still appear, but the inputs are outside the range where the estimate is easiest to defend.

FAQ:

Should I use peak week mileage?

Use a recent steady block instead. Peak week mileage can make the estimate look stronger than the training base that will actually support race day.

Does the split table predict positive or negative splits?

No. The splits assume even effort across the marathon. Adjust them manually if your plan starts slower, finishes faster, or accounts for a hilly course.

Why does the same finish time show different pace units?

The calculation stays on the same marathon distance. Kilometer and mile pace are just two displays of the same adjusted finish time.

When should I use the adjustment slider?

Use it when past marathon results show a consistent personal bias against the baseline estimate. Avoid using it to force a preferred goal from weak inputs.

Can this predict race-day problems?

No. It does not model illness, injuries, fueling mistakes, heat stress, wind, hills, taper quality, or pacing errors.

Glossary:

Average training speed: The typical moving speed from steady aerobic runs used as the speed input.
Checkpoint split: A cumulative projected time at a race marker such as 10 km, halfway, or 40 km.
Model adjustment: A percentage change applied to the baseline finish time to reflect known personal bias.
Race vs training speed: The predicted marathon speed divided by average training speed.
Tanda equation: A training-index marathon prediction equation based on weekly distance, training speed, and run frequency.
Weekly distance: Total running distance in an average week of the training block used for the estimate.

References:

Prediction of Marathon Performance Time on the Basis of Training Indices, Journal of Human Sport and Exercise.
Marathon, World Athletics.
Predicting Marathon Time from Training Characteristics, Open Access Journal of Sports Medicine.