A/B/C goal range
The goal range turns one prediction into an aggressive A goal, realistic B goal, and conservative C goal so race day is not locked to one fragile number.
Race Time Predictor
Use a recent race result to predict a target finish time, compare equivalent race distances, and turn the estimate into aggressive, realistic, and conservative race goals.
Last updated: June 15, 2026
Your run
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Standard Riegel-style profile for recent, comparable road race efforts.
Results
Predicted time
52:07
Target pace
08:23/mi
Prediction confidence and goal rangeHigher confidence
The input and target distances are close enough for a useful pacing target.
- Input and target distances are relatively close.
- Use the realistic goal as a starting pace, then adjust for course and weather.
| Goal | Time | Pace |
|---|---|---|
| A goalAggressive | 51:20 | 08:15 /mi |
| B goalRealistic | 52:07 | 08:23 /mi |
| C goalConservative | 53:25 | 08:35 /mi |
Equivalent race timesRegular profile
| Distance | Time | Pace |
|---|---|---|
| 1 mile | 07:31 | 07:31 /mi |
| 5K | 25:00 | 08:02 /mi |
| 10K | 52:07 | 08:23 /mi |
| 10 mile | 01:26:18 | 08:37 /mi |
| Half marathon | 01:55:00 | 08:46 /mi |
| Marathon | 03:59:46 | 09:08 /mi |
Predicted = known time x (target / known)^1.06 Riegel-style endurance formula. Higher exponents assume more slowdown over longer targets.Equivalent race times
The predictor turns one recent result into equivalent 1 mile, 5K, 10K, 10 mile, half marathon, and marathon estimates so you can compare goal distances before committing to one target.
Runner fatigue profile
Choose beginner, regular, or advanced to change the endurance exponent. Higher exponents create more conservative longer-distance predictions; lower exponents assume less slowdown.
Riegel vs Cameron
This tool uses transparent Riegel-style exponents. Some calculators use Cameron-style variable exponents, so compare predictions as planning ranges instead of treating one formula as exact.
Prediction confidence
The confidence note checks distance similarity, marathon stretch, and profile choice, then widens the goal range when the formula needs more caution.
How this calculator works
Formula
Predicted time = known time x (target distance / known distance)^k, where k is the selected fatigue profile: 1.08, 1.06, or 1.04.
Best use
Estimating similar road race performances, comparing equivalent race times, and choosing a first target pace when fitness, terrain, weather, and pacing are reasonably comparable.
Limitations
Fatigue profiles are planning assumptions. Predictions get weaker when the target is much longer or shorter than the known race, or when terrain, heat, altitude, fueling, and endurance training differ.
Example
A 25:00 5K predicts roughly 52:07 for 10K with the regular 1.06 profile; the beginner profile is more conservative for longer target distances.
Sources and assumptions
- Running Toolkit methodology and sources
Documents the formula choice, unit handling, assumptions, and limits behind this calculator.
- Riegel-style race prediction formula reference
Supports the power-law race-time prediction structure and fatigue exponent context.
How to use it
- Enter a recent race distance and finish time.
- Enter the target race distance or choose a common target.
- Choose a fatigue profile that matches how well prepared you are for the target distance.
- Review the confidence note and A/B/C goal range before choosing your race-day plan.
- Use the equivalent race table to compare 1 mile, 5K, 10K, 10 mile, half marathon, and marathon targets.
- Use the predicted time as a planning range, then adjust for terrain, weather, training, and race-day constraints.
Common mistakes
- Predicting a marathon from a short race without considering endurance preparation.
- Using a workout effort instead of a race or time trial.
- Choosing the advanced profile only because it produces the goal time you want.
- Ignoring course profile, heat, altitude, and fueling differences.
Useful for
- Estimate 10K potential from a recent 5K.
- Choose half-marathon pace from a recent 10K.
- Check whether a goal marathon time is plausible from shorter-distance fitness.
- Compare equivalent race times across common distances before choosing an A, B, and C goal.
Next calculator steps
Convert the prediction with the running pace calculatorTurn the predicted finish time into min/mile, min/km, mph, and kph.Build race splits from the predicted timeUse the B goal as a split plan, then adjust for course and conditions.Open the race planning calculator workflowUse the calculators hub to connect prediction, pace, splits, calories, VO2 max, and heart rate.
Frequently asked questions
How accurate is a race time predictor?
It is a planning estimate. It works best for similar road race distances and conditions, not for trail races, extreme weather, or distances that require very different endurance preparation.
Can I use this as a 5K race time predictor?
Yes. Enter a recent result and choose 5K as the target distance, or enter a 5K result to predict a 10K, half marathon, or marathon.
Can this predict marathon time from a shorter race?
It can estimate a marathon time from a shorter result, but uncertainty rises because marathon performance depends on endurance, pacing, fueling, and training volume.
What recent race should I use?
Use a recent all-out race or time trial on comparable terrain. A stale result or workout effort will usually make the prediction less useful.
Which fatigue profile should I choose?
Use regular for most recent road race results, beginner when the target distance stretches your endurance, and advanced only when your training is specific to the target distance.
How should I use the A, B, and C goals?
Use the A goal only in good conditions, the B goal as the main plan, and the C goal as a fallback when heat, hills, crowding, or fatigue makes the formula result too aggressive.
Why do race predictors give different results?
Predictors use different fatigue assumptions, formulas, and distance limits. Compare the result with recent workouts, long-run durability, conditions, and course profile.
Can this predict a marathon from a 5K?
It can produce an estimate, but the uncertainty is high because marathon performance depends heavily on endurance, fueling, pacing, and long-run preparation.
Related guides
5K time predictor guideUse a recent result to frame realistic 5K targets and pacing.10K time predictor guideTranslate current fitness into 10K finish-time and pace context.Half marathon time predictor guideCheck prediction limits before stretching a shorter result to 13.1 miles.Marathon time predictor guideAccount for endurance, fueling, and durability when projecting marathon goals.