Trail & Ultra-Trail Time Calculator

Estimate your race time with precision

Our trail and ultra-trail time calculator is the most comprehensive tool to prepare your race strategy. Whether you're targeting a 30 km trail or an ultra over 100 km, this tool allows you to estimate your time taking into account all factors that impact your performance.

Import the GPX file of your race for a precise elevation profile analysis, or select from our database of iconic races (UTMB, Western States, Diagonale des Fous...). Our algorithm uses the Minetti polynomial to calculate the real impact of elevation on your pace.

Take into account environmental factors such as altitude, temperature, humidity and night sections. Manage your aid stations with estimated stop times and get a detailed race plan with arrival times at each key point.

Understanding the algorithm: science serving your performance

The Grade-Adjusted Pace (GAP) model

Our calculator uses an energy cost model calibrated on the work of Professor Alberto Minetti (University of Milan), whose research published in the Journal of Applied Physiology is a reference in human locomotion biomechanics. This model calculates the precise impact of slope on your pace:

• Climb 0-8%: running zone, metabolic cost increases quasi-linearly (+11.5% per percentage point)
• Climb 8-15%: transition to power hiking, multiplier reaches 2.8x for elites
• Climb 15-25%: mandatory fast walking, energy cost multiplied by 4 to 4.5
• Beyond 25%: extreme terrain where even the best walk slowly (6x and more)

On descents, the model also integrates biomechanical complexity: a moderate slope (-5 to -10%) allows speed gain, but steep descents increase eccentric muscle work and neuromuscular fatigue.

Fatigue modeling in ultra-trail

Ultra-distance fatigue follows an exponential model validated by field data (calibrated on UTMB, CCC, Western States). Parameters vary according to your experience level:

• Beginner runner: fatigue onset around 15 km, speed loss can reach 40%
• Intermediate runner: onset around 25 km, maximum 30% slowdown
• Advanced runner: onset around 35 km, plateau at 25%
• Elite runner: can maintain pace up to 50 km with only 18% maximum degradation

This model also integrates ultra and extreme thresholds: beyond certain distances (varying by level), fatigue accelerates due to glycogen depletion and accumulated muscle micro-damage.

Altitude impact on performance

Above 2000 m, the decrease in oxygen partial pressure significantly degrades aerobic capacity. Our model applies a +2% penalty per 300 m of altitude above this threshold, in accordance with Chapman et al. studies on altitude hypoxia. Acclimatization reduces this impact:

• 3 days at altitude: 30% impact reduction
• 7 days: 50% reduction
• 14 days: 70% reduction
• 21 days and more: 85% reduction

Circadian rhythm and night running

Studies by Reilly and Waterhouse on sports chronobiology show that performance fluctuates significantly over a 24-hour cycle. Our algorithm integrates your chronotype (early bird, intermediate, night owl) and start time to calculate circadian impact. Night running incurs a minimum +15% penalty, increased by +5% per terrain technicality level due to reduced vision and altered optical flow.

Pacing strategy: keys to trail success

The constant effort principle

The most effective strategy in trail and ultra-trail is constant effort (same perceived effort) rather than constant pace. This means:

• Slow down on climbs to maintain stable heart rate (typically 70-80% of max HR)
• Accelerate moderately on descents if terrain allows, without exceeding 85% of max HR
• Adapt pace to conditions: heat, altitude, accumulated fatigue

Classic mistakes to avoid

• Starting too fast: start-line euphoria leads to overestimating capabilities. The first 10 kilometers should be run 5-10% slower than your target pace.
• Neglecting descents: they generate significant muscle damage. Save yourself early in the race.
• Ignoring body signals: intense thirst, developing cramps, loss of concentration are warnings to take seriously.

Aid station management

Time spent at aid stations represents 10 to 15% of total time on an ultra. Our calculator automatically adapts stop times according to your level:

• Elite: 2-3 minutes (grab & go with assistance)
• Advanced: 5-8 minutes (efficient routine)
• Intermediate: 9-14 minutes (taking time, checking equipment)
• Beginner: 15-23 minutes (longer rest, stress management)

Nutrition and hydration: the fuel of performance

Scientific basis of exercise nutrition

Our nutritional model is based on the latest publications from the International Society of Sports Nutrition (ISSN 2019) and field observations from major ultra-trails (study PMC12501108). Theoretical recommendations of 60-90 g/h of carbohydrates are rarely achievable in the field: ultra-runners consume on average 20-40 g/h.

Personalized carbohydrate intake

The calculator automatically adapts your carbohydrate needs according to:

• Estimated duration: from 20 g/h for short efforts (<1h30) to 60-75 g/h for ultra-long (>12h)
• Gender: women require about 25% less carbohydrates due to smaller stomach volume and slower gastric emptying (First Endurance 2024)
• Intensity: at 50% of MAS, the body mainly uses lipids; at 80% of MAS, carbohydrates become the main fuel
• Gut training: without specific preparation, absorption limit is 45 g/h; with a trained gut and glucose-fructose mix (2:1 ratio), you can reach 90 g/h

Energy expenditure in trail

Our energy calculation formula, based on Minetti et al. research, integrates three components:

• Horizontal cost: 1.05 kcal/kg/km (flat running)
• Positive elevation cost: +0.65 kcal/kg per 100 m of D+
• Negative elevation cost: +0.35 kcal/kg per 100 m of D- (eccentric muscle work)

Concrete example: a 70 kg runner on 100 km with 5000 m of D+ will expend approximately 12,000 kcal, equivalent to 5-6 days of normal food intake.

Hydration adapted to conditions

Fluid needs vary considerably depending on climate and pace. Our algorithm calculates your needs based on:

• Climate conditions: from 350 ml/h (optimal conditions 5-15°C) to 850 ml/h (extreme heat >30°C)
• Pace: a slow runner (>8 min/km) sweats 30% less than a fast runner (<5 min/km)
• Body weight: normalized for a 70 kg athlete

Beware of hyponatremia risk: drinking too much can be as dangerous as not drinking enough. In cool conditions and slow pace, don't exceed 500 ml/h.

Electrolytes and sodium

Sodium loss through sweat varies from 200 to 600 mg/h depending on conditions and intensity. In hot conditions (>25°C) and prolonged efforts (>4h), electrolyte supplementation becomes crucial:

• Count 1 to 2 electrolyte tablets per hour (about 300 mg sodium each)
• Prefer isotonic drinks containing 500 mg sodium per liter
• On ultra-long efforts, alternate sweet and salty to maintain appetite

Preventing the glycogen "wall"

The famous "wall" occurs when muscle glycogen stores (about 2000 kcal) are depleted. To avoid it:

• Start eating within the first 30 minutes
• Maintain regular intake every 20-30 minutes
• On ultra, eat at aid stations even without feeling hungry
• Vary textures: gels, bars, dried fruits, savory sandwiches

Scientific references

Our algorithm is based on the following publications:

• Minetti, A.E. et al. (2002). "Energy cost of walking and running at extreme uphill and downhill slopes". Journal of Applied Physiology.
• ISSN Position Stand (2019). "Carbohydrate for endurance athletes". Journal of the International Society of Sports Nutrition. PMC6839090.
• Stuempfle, K.J. et al. (2011). "Race diet of finishers and non-finishers in a 100 mile (161 km) mountain footrace". Journal of the American College of Nutrition. PMC12501108.
• First Endurance (2024). "Gender differences in ultra-endurance nutrition".
• Chapman, R.F. et al. (2014). "Effect of altitude on running performance". Medicine & Science in Sports & Exercise.
• Reilly, T. & Waterhouse, J. (2009). "Circadian rhythms and exercise performance". Sports Medicine.