Formula, in endurance
Race-Week Taper Formula + Carb Loading (Burke)
Tapering cuts training volume sharply while keeping intensity and the number of sessions. Bosquet's 2007 meta-analysis of 27 studies found the best results from a 2-week taper that reduces volume exponentially by 41–60%, with intensity and frequency unchanged. Mujika & Padilla's review puts the usual gain at about 3% (range 0.5–6%). The taper withdraws fatigue, not fitness.
4 variables. Published May 14, 2026. Updated Oct 19, 2026. By AI Fit Hub.
taper_week_volume = peak_volume × (1 − average_cut × shape_week)
average_cut = 0.41 (5K) to 0.60 (ultra), inside the 41-60% range
shape = [1] for 1 week, [0.8, 1.2] for 2 weeks, [0.7, 1.0, 1.3] for 3 weeks
intensity and run frequency kept throughout Variables
peak_volume
Peak training volume
Highest weekly volume during build phase (km, hours, or distance equivalent). The taper starts from here.
average_cut
Average volume cut
Share of peak volume removed, averaged over the taper weeks: 0.41-0.60 per the meta-analysis. The calculator uses 41% for a 5K up to 55% for a marathon and 60% for an ultra.
shape_week
Weekly shape factor
Spreads the average cut so it deepens toward race day; the factors average 1, so the weeks average the headline cut.
intensity
Training intensity
Pace, power, or RPE of quality sessions. Keep it at race intensity through the taper; cut how long each session is, not how hard. Cutting intensity (the common mistake) erodes fitness; cutting volume preserves it while clearing fatigue.
Step by step
- 1
Take your peak weekly volume from the build (the highest week, not the average).
Marathon training peaked at 80 km a week.
- 2
Choose the taper length; 2 weeks was the most effective on average in Bosquet's meta-analysis.
Marathon: a 2-week taper starting 14 days out.
- 3
Compute each week's volume from the average cut and its shape.
Marathon average cut 55%: 0.8 × 55% = 44% two weeks out, 1.2 × 55% = 66% in race week → 80 × 0.56 = 44.8 km and 80 × 0.34 = 27.2 km.
- 4
Keep the quality sessions at race pace and shorten them.
Two weeks out: marathon-pace tempo and an interval session, both shorter. Race week: one short race-pace session with strides.
- 5
Keep the number of runs; shorten the easy runs and the long run.
Longest run 20.2 km two weeks out and 12.2 km in race week.
Worked example
A marathon runner peaking at 80 km a week, race in 14 days
Peak volume
80 km/week
Taper length
2 weeks
Race
Marathon
Two weeks out: 80 × (1 − 0.44) = 44.8 km, longest run 45% of that = 20.2 km Race week: 80 × (1 − 0.66) = 27.2 km plus the race, longest run 12.2 km Average cut: (44% + 66%) / 2 = 55%
44.8 km two weeks out (a 44% cut) with a 20.2 km long run, then 27.2 km in race week (a 66% cut) with a 12.2 km long run, for a 55% average cut. Quality sessions keep their pace and every usual run stays in the week, only shorter.
Common variations
Run the numbers next
- Cardio Running Pace Calculator
Calculate pace per km and mile and project race finish times from one run.
- Cardio Race Time Predictor
Race Time predictor: predict finish times across 5K, 10K, half marathon, and marathon from any known race result using Riegel's formula.
- Cardio Marathon Pace + Elevation Calculator
Convert a target marathon time on a hilly course into the flat-equivalent pace you actually need.
Questions people ask next
How much should you cut training volume during a taper?
By 41–60% of peak volume, reduced progressively. That was the most effective range in Bosquet's 2007 meta-analysis of 27 studies, with training intensity and frequency left unchanged.
How long should a taper be?
About 2 weeks was most effective on average (Bosquet 2007). Mujika & Padilla's review reports effective tapers from 4 days to more than 28 days, so shorter races and lower training loads can use the short end.
How much faster does tapering make your race?
Performance usually improves by about 3%, with a usual range of 0.5–6%, according to Mujika & Padilla's 2003 review. Bosquet's meta-analysis reports its results as effect sizes rather than percentages.
How much carbohydrate should I eat before a race?
For events lasting more than 90 minutes, the 2016 sports-nutrition position stand advises about 10–12 g of carbohydrate per kg of body weight a day for the 36–48 hours before (Thomas 2016). During the race, Burke 2011 advises 30–60 g an hour for longer events and up to 90 g an hour beyond 2.5 hours.
What is the most common tapering mistake?
Cutting intensity along with volume. The most effective tapers in Bosquet's analysis kept intensity unchanged and removed volume, so keep the pace of the hard sessions and shorten everything else.
Sources
- Mujika I & Padilla S (2003). Scientific bases for precompetition tapering strategies. , Medicine & Science in Sports & Exercise — review of taper design and the usual 3% gain
- Bosquet L et al. (2007). Effects of tapering on performance: a meta-analysis. , Medicine & Science in Sports & Exercise — 27 studies
- Thomas DT, Erdman KA & Burke LM (2016). Position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine: nutrition and athletic performance. , Journal of the Academy of Nutrition and Dietetics — carbohydrate loading
- Burke LM et al. (2011). Carbohydrates for training and competition. , Journal of Sports Sciences — carbohydrate during competition