Free Tool

Race Time Predictor

Guna satu race yang anda dah lari untuk predict masa finish kat jarak lain. Formula Riegel, plus pace dan table penuh untuk semua jarak standard.

Race you have already run

Your most recent all-out race. A training run at 80 percent effort will give you a prediction you cannot hit.

Race you want to predict

This sets the fatigue exponent. It barely matters between 5K and 10K, and it matters a lot when you predict a marathon from anything short.

How race prediction works

Predicting a finish time at one distance from a result at another rests on a simple observation: the pace a runner can hold drops in a fairly predictable way as distance grows. The standard model raises the distance ratio to a fixed exponent, which lands close enough for most runners to be useful. It is a starting point for goal setting, not a guarantee.

When predictions hold up, and when they do not

They are most accurate when the distances are close together, when the race you enter was run recently at full effort, and when your training actually supports the target distance. Predicting a 10K from a 5K is usually within a minute. Predicting a marathon from a 5K is almost always optimistic, because the marathon exposes endurance and fuelling limits a 5K never touches. If you have not run the long runs, the prediction is describing a version of you that does not exist yet.

Adjust for the conditions you will actually race in

Predictions assume the target race runs in similar conditions to the one you entered. That rarely holds here. A time set on a cool December morning will not repeat in March at 85 percent humidity. Run the predicted pace through the Heat and Humidity Pace Adjuster before you commit to a goal, then build your pace band from the adjusted number.

What to do with the number

Treat the prediction as the ceiling of what is possible on a good day, then set your actual race plan a little inside it. Runners who race at exactly their predicted pace from the gun tend to find out in the last quarter whether the prediction was right. Runners who start slightly inside it usually finish faster.

Common questions

How accurate is a race time predictor?

Within about one to two percent when the two distances are close and the input race is recent and hard. The error grows quickly as the gap widens, so a half marathon predicted from a 10K is reasonable while a marathon predicted from a 5K should be treated as a best case scenario.

Why is my marathon prediction so much faster than what I ran?

Because the model only knows your speed, not your endurance. Marathon performance depends on long run volume, fuelling and pacing discipline, none of which appear in a 5K result. If your longest run is 15 km, the prediction is describing potential rather than readiness. Set the endurance option to the third choice and the number will come back closer to reality.

What does the endurance setting actually change?

The exponent in the formula. The standard value of 1.06 assumes a runner with reasonable endurance for the distance they are predicting. Lowering it to 1.05 suits someone with a deep aerobic base and consistent long runs. Raising it to 1.08 suits someone whose speed is ahead of their mileage. The further apart the two distances are, the more this choice moves the answer.

Which race should I enter into the predictor?

The most recent race you ran at full effort, within the last six weeks or so. If you have results at several distances, use the one closest to the distance you are predicting.

Should I set my race goal at the predicted time?

Set it slightly inside. Give yourself a target you can commit to from the start and a stretch goal for the last third if the day is going well. Chasing the exact predicted pace from kilometre one leaves no room for heat, hills or a bad stomach.

Does the prediction account for Malaysian weather?

No. It assumes similar conditions in both races. Put the result through the Heat and Humidity Pace Adjuster to get a target that reflects the temperature and humidity you will actually be racing in.

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