Vertical Fuel

Trail & ultra fuelling

The fuel plan that counts the climbing.

Put in your expected time, your climb and the temperature. You get carbohydrate, fluid and salt per hour, a schedule, and a packing list in gels, bars and salt capsules.

  • Free, no account
  • Nothing leaves your browser
  • Reads your race's GPX
Build my plan See a race page
Start from a known race

Fills in the distance, the climb and a rough finishing time. You can change all of it afterwards.

Or load the race's GPXoptional

Most organisers publish a .gpx of the course. Drop it in and the distance, the climb and the profile are read from it. If the file names the aid stations, you also get a plan per leg. The file stays in your browser.

Step 1 of 5

Your race

How long you expect to be out, how much you climb, how warm it gets and how much you weigh. Distance only feeds the time estimate.

Not sure how long it will take you?work it out

Give it your flat pace and it works out a time from your distance and climb.

100 m of climb counts as 1 km of flat running. It is a rule of thumb. If you have your own splits, trust those.

6 °C to 14 °C

◀ coldest 6 °C14 °C warmest ▶

Cool

Drag the second handle if the temperature will change during the day.

Units

Step 2 of 5

Per hour

80g Carbohydrate per hour range 60–90 g
  • Fluid 450ml
  • Sodium 450mg
  • Energy from carbohydrate 320kcal

Step 3 of 5

Hour by hour

Drag along the profile to move through the race. The markers are when you eat and drink.

  • Gel, bar or chews
  • Refill the flask
  • Salt capsule

3.5 h · 2,050 m of climbing

At0:00
Next upGel in 20 min
Taken by then0 g carb
Fluid drunk0.0 L

Without a GPX the profile is a sketch drawn from your total climb, not your actual course. The times are real.

    Put it on your watch

    Set these repeating alerts on your watch and it buzzes you at the right times.

      Where the setting lives on your watch
      Garmin
      Start the run, hold MENU → Alerts → Add New → Custom → Eat or Drink. Time or distance, and you can name each one.
      Coros
      Run activity → Activity Alerts → Nutrition Alerts. Time only, not distance.
      Polar
      Run activity → Fueling → Manual Carbs Reminder, plus a separate drinks reminder. Its Smart Carbs Reminder will also work an interval out for you.
      Apple Watch
      No nutrition alert of its own. Workout app → the bell icon → a repeating Time alert, or use an app like WorkOutDoors for named ones. The calendar file below is the better route here.

      Step 4 of 5

      In the vest

      Tick things off as you pack. Set the sizes to the products you carry.

        0 of 4 packed

        Your products

        One scoop is assumed per 500 ml of drink.

        Step 5 of 5

        Take it with you

        The whole plan is in the address of this page. Copy the link and send it to yourself or your crew.

        Put the schedule in your calendar

        One calendar event per gel, refill and salt capsule, each with an alarm. Import it on your phone and the alarms reach your watch.

        Events are five minutes long with the alarm on the minute. Times are local, so another time zone still works.

        Have it emailed to you

        Products

        Where to buy

        The plan does not depend on a brand. These are places to buy what it asks for.

        Sources

        Where the numbers come from

        Every figure on this page is either from published research, with the source named, or from common coaching practice, marked as such.

        Read the evidence and the ten sources
        • Carbohydrate. The joint position stand of the American College of Sports Medicine, the Academy of Nutrition and Dietetics and Dietitians of Canada gives 30–60 g an hour for efforts of one to two and a half hours, and up to 90 g an hour beyond that. Under about 45 minutes nothing is needed.1 One sugar on its own is absorbed at about 60 g an hour at most, so anything above that has to mix glucose and fructose.2
        • The ratio. Most gels still advertise 2:1 glucose to fructose. A meta-analysis of 14 studies found the best delivery and performance closer to 1:0.8, and a 2022 review agreed and found the near-equal ratio easier on the gut.3
        • 120 g an hour. In a 2020 study, elite runners at a 42 km mountain marathon with 3,980 m of climbing took 60, 90 or 120 g an hour. Of 31 starters, 20 finished, and only finishers were analysed, so six or seven runners per group.4 A trial in 11 cyclists found 120 g was burned faster than 90 but did not spare the body's own glycogen and did not measure performance.5 No study has shown that 120 g an hour is faster than 90. It is a ceiling for trained athletes, not a target.
        • Gut training. Four to six weeks, one or two fuelled hard sessions a week, adding about 10 g an hour every one to two weeks, with the products you will race with. This is coaching practice, not a trial result.
        • Sweat. Across 506 athletes, sweat rate averaged 1.2 litres an hour but ranged from 0.26 to 5.73. Sweat sodium averaged about 1,000 mg per litre, with values from under 300 to over 2,400.6 That is why the calculator gives a band rather than a number.
        • Sweat sodium cannot be predicted. A 2022 analysis using individual, environmental and dietary factors explained only 17–23 % of the variation between people.7 The only way to know yours is to measure it.
        • The fluid and sodium bands. 300–500 ml an hour in the cold, 600–800 in the heat, and 300–600 mg of sodium an hour past 90 minutes are the ranges in common coaching use. They are starting points. No consensus statement sets an hourly sodium target, and the 2026 cycling nutrition consensus declines to give one.8
        • Drinking too much is the dangerous error. Exercise-associated hyponatremia, where blood sodium is diluted by drinking more than you sweat, has killed endurance athletes. The international consensus recommends drinking to thirst and states that fixed intake ranges are not appropriate.9 Salt tablets do not prevent it. Take salt to replace what you sweat, not as a reason to drink more.
        • Why it ignores your watch. A 2022 systematic review of 42 wrist devices from 23 manufacturers found an average error above 30 % for every brand, and from 15 % to 211 % across studies of one model. None was accurate enough for energy expenditure.10 Duration, climb and temperature are rougher inputs, but they are not wrong by a factor of two.

        Sources

        1. Thomas, D. T., Erdman, K. A., & Burke, L. M. (2016). Position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and Athletic Performance. Medicine & Science in Sports & Exercise, 48(3), 543–568. doi:10.1249/MSS.0000000000000852 Joint position stand of three professional bodies.
        2. Podlogar, T., & Wallis, G. A. (2022). New horizons in carbohydrate research and application for endurance athletes. Sports Medicine, 52(Suppl 1), 5–23. doi:10.1007/s40279-022-01757-1 Review.
        3. Rowlands, D. S., Houltham, S., Musa-Veloso, K., Brown, F., Paulionis, L., & Bailey, D. (2015). Fructose–glucose composite carbohydrates and endurance performance: critical review and future perspectives. Sports Medicine, 45(11), 1561–1576. doi:10.1007/s40279-015-0381-0 Meta-analysis of 14 studies.
        4. Viribay, A., Arribalzaga, S., Mielgo-Ayuso, J., Castañeda-Babarro, A., Seco-Calvo, J., & Urdampilleta, A. (2020). Effects of 120 g/h of carbohydrates intake during a mountain marathon on exercise-induced muscle damage in elite runners. Nutrients, 12(5), 1367. doi:10.3390/nu12051367 20 finishers, 6–7 per group.
        5. Podlogar, T., Bokal, Š., Cirnski, S., & Wallis, G. A. (2022). Increased exogenous but unaltered endogenous carbohydrate oxidation with combined fructose-maltodextrin ingested at 120 g h⁻¹ versus 90 g h⁻¹ at different ratios. European Journal of Applied Physiology, 122(11), 2393–2401. doi:10.1007/s00421-022-05019-w 11 trained cyclists.
        6. Baker, L. B., Barnes, K. A., Anderson, M. L., Passe, D. H., & Stofan, J. R. (2016). Normative data for regional sweat sodium concentration and whole-body sweating rate in athletes. Journal of Sports Sciences, 34(4), 358–368. doi:10.1080/02640414.2015.1055291 506 athletes. Whole-body sweating rate was estimated from regional patches, not measured directly.
        7. Baker, L. B., De Chavez, P. J. D., Nuccio, R. P., et al. (2022). Exploring the role of individual, environmental and dietary factors in sweat sodium concentration. Journal of Applied Physiology. doi:10.1152/japplphysiol.00391.2022
        8. Jeukendrup, A. E., Redegeld, M., Martins, G., et al. (2026). UCI Sports Nutrition Project: Race nutrition for road cycling. International Journal of Sport Nutrition and Exercise Metabolism, 36(3), 215–232. doi:10.1123/ijsnem.2025-0239 Expert consensus.
        9. Hew-Butler, T., Rosner, M. H., Fowkes-Godek, S., et al. (2015). Statement of the Third International Exercise-Associated Hyponatremia Consensus Development Conference, Carlsbad, California, 2015. Clinical Journal of Sport Medicine, 25(4), 303–320. doi:10.1097/JSM.0000000000000221 International consensus statement.
        10. Germini, F., Noronha, N., Borg Debono, V., et al. (2022). Accuracy and acceptability of wrist-wearable activity-tracking devices: systematic review of the literature. Journal of Medical Internet Research, 24(1), e30791. doi:10.2196/30791 Systematic review, 42 devices from 23 manufacturers.

        Links go to the publishers. Where a paper is behind a paywall, the abstract carries the figure quoted. The note after each source says what kind of evidence it is, so you can weigh it yourself.

        Questions

        Common questions

        Why doesn't this use the calories from my watch?

        The estimates are too rough. A 2022 review of 42 wrist devices found an average error above 30 % for every brand, and up to 211 % for one model. Burning 500 calories also does not raise your needs by 500; the body compensates, and by a different amount in each person. (Source 10.)

        How many carbohydrates per hour do I need?

        Under an hour, none if you started fed. One to two hours, 30–60 g. Beyond two hours, 60–90 g, and trained athletes can go higher. Above 60 g only works if the gel or drink mixes glucose and fructose. Look for a ratio near 1:0.8 rather than 2:1.

        Is 120 grams an hour realistic?

        It is real, but it is the ceiling and it takes preparation. In a 2020 mountain marathon study, elite runners took 60, 90 or 120 g an hour. 20 of 31 finished, and three who dropped out had stomach trouble. The authors concluded that 120 g an hour can be absorbed by elite runners who have trained for it. Start where you are and build. (Source 4.)

        How do I train my gut?

        Four to six weeks. One or two hard sessions a week, adding about 10 g an hour every one to two weeks, always with the products you will race with. A gut trained on one brand is not trained on another.

        How much should I drink?

        Sweat rates run from 400 to over 2,500 ml an hour, so any single number is a guess. Start with 300–500 ml an hour below 15 °C and 600–800 above 25 °C. Then drink to thirst, and never more than the sweat rate you have measured.

        How do I measure my sweat rate?

        Weigh yourself naked. Run an hour at your normal pace and note everything you drink. Towel off and weigh again. Sweat rate is weight lost plus fluid drunk. Do it once in the cold and once in the heat. The two numbers will differ.

        Do I need salt tablets?

        Under an hour, no. From 60 to 90 minutes they are insurance. Past 90 minutes, 300–600 mg of sodium an hour is the range in common use, more if it is hot or you sweat salty. Sweat sodium varies from under 300 to over 2,400 mg per litre, so the average says little about you. Salt does not protect you from drinking too much.

        What is the dangerous mistake?

        Drinking too much. Exercise-associated hyponatremia has killed marathon runners. The risk is highest past four hours, for smaller athletes, and for anyone drinking to a schedule instead of thirst. If a number here looks high to you, go lower.

        Does it work for cycling or hiking?

        The carbohydrate guidance is the same. It depends on duration and intensity, not the sport, and the researcher behind the guidelines says the advice for cyclists and runners should not differ. The idea that cyclists can eat more because the gut is shaken less is not established. The one trial that matched the two sports for effort found no difference in gut symptoms. Use the same numbers and let your own gut decide.

        Legal

        The small print

        Affiliate disclosure

        Some links on this site are affiliate links. If you buy through one, the retailer pays me a small commission at no extra cost to you. It changes nothing about what the calculator tells you: the numbers come from published research on carbohydrate, fluid and sodium intake, and no brand has any say in them. Products are listed because they fit the plan, not because of what they pay.

        Privacy

        The calculator sends nothing anywhere. Every number you type is worked out in your own browser. Nothing is stored on your device and nothing reaches a server. Your inputs live only in the address of the page, which is what makes a plan shareable as a link.

        If you enter your email to have a plan sent to you, that address goes to my email provider and is used only to send you what you asked for and occasional notes about race fuelling. It is not sold or shared. Every email has an unsubscribe link, and you can ask me to delete your address at any time.

        Cookies. This site sets no tracking cookies of its own. If you click an affiliate link, the retailer may set a cookie so a purchase is credited to this site. That happens on their domain and is covered by their privacy policy.

        Fonts are loaded from Google Fonts, which means Google receives your IP address when the page loads. If you would rather it did not, write to me and I will self-host them.

        Terms of use

        This site is free to use and is provided as it is, with no warranty. The calculator produces population-level estimates for healthy adults, based on published guidance. It is not medical or dietary advice and is not a substitute for a doctor, a dietitian or your own experience.

        Endurance events carry real risk, and getting fuelling or hydration wrong can be dangerous, drinking beyond your sweat rate in particular. You are responsible for what you eat and drink, and for rehearsing any plan in training before you race on it. If you have a medical condition, are pregnant, or take medication that affects fluid balance, speak to a doctor rather than a calculator.

        The content on this page is mine; you are welcome to link to it, and not to republish it wholesale. Contact: add your email address.

        Read this before you race on it. These are population ranges, not a prescription. Exercise-associated hyponatremia, drinking more than you sweat, has killed marathon runners and is the more dangerous error for most recreational athletes, particularly those out for four hours or more. Nothing new on race day: everything here should be rehearsed in training first. If you have a medical condition or take medication that affects fluid balance, talk to a doctor rather than a calculator.