Race Taper Calculator
A taper plan for the weeks before a race — how much to cut your weekly volume, week by week, for a 5K through to a marathon or an Ironman — from your peak training week.
A taper sheds fatigue while keeping fitness: volume comes down 40–60% over one to three weeks while intensity stays, because it is the mileage that tires you and the fast work that keeps you sharp.
How the race taper calculator works
A taper sheds fatigue while keeping fitness: volume comes down 40–60% over one to three weeks while intensity stays, because it is the mileage that tires you and the fast work that keeps you sharp. Shorter races need a shorter taper; a marathon or Ironman takes three weeks. The plan here uses the pattern reviews of tapering studies support — a progressive cut, biggest in the final week — applied to your peak weekly volume.
Formula: taper week volume = peak volume × (80%, 60%, 40%) over three weeks, or (75%, 50%) over two, or 60% over one
Worked examples
| Inputs | Taper length | Note |
|---|---|---|
| Marathon, 70 km peak | 3 weeks | 56, 42, 28 km |
| Half marathon, 40 miles peak | 2 weeks | 30, 20 miles |
| 5K, 8 hours a week | 1 week | 4.8 hours in race week |
FAQFrequently asked questions
Why keep intensity?
Fitness is lost slowly but sharpness is lost quickly; short fast efforts keep the neuromuscular system and running economy tuned without adding fatigue. Cutting everything leaves people feeling flat on race day.
I feel sluggish in the taper — is that normal?
Very. Legs often feel heavy in the second week as the body repairs; it passes. Trust the plan rather than adding a hard session to feel better.
Should I change what I eat?
Keep eating normally — you are still training, just less — and increase carbohydrate in the last two or three days before a long race. Do not diet in the taper.
What about the day before?
Rest or a very short easy session with a few strides. Sleep matters most two nights before the race, since the night before is often poor.
Where these figures come from
- Riegel PS, "Athletic records and human endurance", American Scientist 1981 — T2 = T1 × (D2 ÷ D1)^1.06
- Cooper KH, "A means of assessing maximal oxygen intake", JAMA 1968 — the 12-minute run test
- Ainsworth BE et al., Compendium of Physical Activities (2024 update) — MET values by activity
- OpenPowerlifting — DOTS coefficients (Tim Konertz, 2019) — the DOTS polynomial used for scoring
- Naismith's rule (1892) as used by UK and Australian walking bodies — 1 hour per 5 km plus 1 hour per 600 m of ascent
- UK Sport — national high-performance body
Last checked: September 2026. Formulas are fixed by their published sources; the MET values come from the Compendium of Physical Activities.