Marathon Training Plan Calculator
Work backward from race day into editable base, build, peak and taper phases without inventing mileage or workout prescriptions. Sensitive inputs stay in your browser.
Four user-entered phases lead to race day on Dec 14, 2026 without prescribing mileage or workout intensity.
Context matters.
- This is a phase calendar, not a training prescription. Use a qualified plan or coach for weekly mileage, workout type, strength, recovery and race readiness.
- The B.A.A. describes its plans as guides and advises appropriate medical judgment; personal history and current symptoms control.
Sources & scope
The calculation guide and this source trail show what the result means, where the rule came from and when it was last reviewed. This is source-and-calculation QA, not a claim of medical, legal, tax or other professional review; time-sensitive decisions still belong with the linked authority.
A visible path from input to answer.
Work backward from race day into editable base, build, peak and taper phases without inventing mileage or workout prescriptions. The page keeps the calculation scope and its limits beside the result so the output can be checked, copied or revisited.
- Read the record. The calculator uses Race date, Plan length (weeks), Base phase (weeks), Build phase (weeks) and Peak phase (weeks) and 3 additional fields supplied in the form.
- Apply the scope. It applies the Runner-entered marathon phase calendar — qualified plan, coach, health history and current symptoms control training load reference and the explicit date, unit and counting conventions shown in the result.
- Expose the checkpoints. Intermediate rows, warnings and timeline events stay visible; the emphasized row identifies the primary checkpoint when one exists.
Four user-entered phases lead to race day on Dec 14, 2026 without prescribing mileage or workout intensity.
- Race dayDec 14, 2026
Calculation purpose: Work backward from race day into editable base, build, peak and taper phases without inventing mileage or workout prescriptions. This is a high-sensitivity reference output; the linked authority or qualified professional controls the final decision.
Calendar inputs use plain year-month-day semantics. Leap days, month ends, date-pair order and unsupported dates are checked before the result is shown.
Rule set 1.1.0 · Last reviewed 2026-08-22 · Next review due 2027-02-22. The source panel below contains the linked evidence.
What to know before using the result.
How is the marathon plan start date calculated?
CalcSpan subtracts the entered plan length in whole weeks from race day and divides that range into your editable base, build, peak and taper phases.
Does the calculator prescribe weekly mileage?
No. It is a phase calendar only; a qualified plan or coach should set mileage, workouts, recovery and race readiness.
Why must the phase lengths equal the total plan length?
That validation prevents gaps or overlaps between the four calendar phases leading to race day.