What this result means
Required performance tells you the clock you need at a known distance. Feasibility tells you how far a goal sits from what your current race already implies. Enter current distance and time, goal distance and time. The tool predicts the goal distance from the current race, then sees how much faster the goal is than that prediction.
Bands: already there (goal slower or equal to prediction), close (up to 2% faster), stretch (2–8%), outlier (more than 8%). Those cut-points are lab conventions, not physiology.
A 46:20 10K predicting ~1:42 half makes a 1:42 goal “already there” on Riegel. A 1:30 half from that 10K is a large percent and will show as an outlier. A 1:40 half from 1:42 predicted is a small stretch.
A current marathon slower than a goal 10K is a nonsense pair; the model will still compute a percent. Use nearby distances.
Calculation method
Predicted goal time = Riegel from current race to goal distance. Improvement percent = (predicted − goal) / predicted × 100. Positive means the goal is faster than the prediction.
Same Riegel 1.06 as the predictor. Not VDOT.
A “close” band does not mean you will hit it next month. Training, health, and the course decide. An outlier can still happen with years of work; the label is about the gap on this formula, not your character.
Frequently asked questions
What does stretch mean?
The goal is 2–8% faster than what Riegel predicts from your current race. It is a gap size, not a training plan.
How is this different from required performance?
Required performance returns a clock at a known distance. Feasibility returns how large the gap is toward a goal clock.
Does this use VDOT?
No. Feasibility is inverse comparison against Riegel. VDOT lives on equivalents and VO2-from-race.