Free tool

Gel Calculator

How many gels do you need for your ride or run? Pick your hours and ride type. You get total carbs, gels to carry and a timing plan. No signup.

General guidance only, not medical advice. Ride numbers come from the chart in my free DIY Fuel Guide. Run numbers come from published sports-nutrition guidelines (see Sources). If you have a health condition or specific dietary needs, check with your doctor or a dietitian first.

Activity Ride Run

Ride type

Hours (for example 2.5)

Body weight (optional, for the pre-ride meal)

Weight only changes the meal before you start (1 to 4 g/kg, 1 to 4 h before). Carbs during exercise stay in grams per hour and are not scaled by weight. Not saved anywhere.

Carbs per gel, in grams

25 g is my estimate for one homemade gel (the guide's number), not a lab measurement. It is just a starting value: change it to match your gel. Check the label if you buy gels.

Gel timing

Auto picks the slowest pace in this list that still reaches the low end of the carbs per hour range. With a 25 g gel, 30 to 60 g/h is a gel about every 25 to 50 minutes, and 60 to 90 g/h is about every 17 to 25 minutes. My timing post says start within about 45 minutes, then one gel every 30 to 45 minutes.

Your plan

The chart behind it (rides)

From the DIY Fuel Guide, "By ride type (per hour)". Fluid and sodium are in the guide too, so they are shown here for reference. They are starting points, not sourced targets. Climbs / hilly follows the published duration bands (30 to 60 g/h up to 2.5 h, 60 to 90 g/h past 2.5 h).

Ride	Carbs/h	Fluid/h	Sodium/h

The chart behind it (runs)

By run length, from the ACSM / Academy of Nutrition and Dietetics / Dietitians of Canada joint position statement (2016), which Burke et al. (2011) matches. The sources give no run-specific fluid or sodium numbers, so those say "Varies; follow your plan".

Run length	Carbs/h	Fluid/h	Sodium/h

The source bands "45 to 75 min" and "1 to 2.5 h" overlap. This calculator switches at 1 h. The 60 g/h low end for 2.5 h+ is my pick (the top of the 1 to 2.5 h band); the source only says "up to 90 g/h".

Running: what is different

Carbs per hour are the same idea for runners and riders. Jeukendrup (2014): "Exogenous carbohydrate oxidation appears to be similar in cycling and running, suggesting that the advice for cyclists and runners is not different." So run mode is organised by how long you run, not by a lower number.
The gut is the difference. de Oliveira, Burini and Jeukendrup (2014): "symptoms are more common in runners than in cyclists," thought to come from "the repetitive high-impact mechanics of running." In a questionnaire study of well-trained long-distance runners, 71% reported lower-gut symptoms (bloating, cramps, urge to defecate) and 36% upper-gut symptoms (nausea, belching) during exercise (Peters et al., 1999).
Train the gut. Athletes "not accustomed to fluid and food ingestion during exercise had a twofold risk of developing gastrointestinal symptoms" (de Oliveira 2014). In a 2023 systematic review, about 2 weeks of repeated carbohydrate feeding during exercise cut gut discomfort by an average of 47% (2 studies, Martinez et al.).
Should runners start lower? The sources do not give runners a lower number. They do say amounts "may need to be adjusted downward" at low absolute intensity, and that a runner finishing a marathon in 5 h "would not necessarily need" 90 g/h (Jeukendrup 2014). My practical take, not a study result: start near the low end of your range on training runs and build up, and never try anything new on race day.
Above about 60 g/h the position statement points to products with a glucose + fructose mix ("multiple transportable carbohydrates"), though it notes the evidence for special blends is still limited.
Fluid and sodium: no run-specific numbers in the sources, so follow your own plan. General ACSM / AND / DC (2016): sweat rates run 0.3 to 2.4 L/h; a plan of 0.4 to 0.8 L/h suits most athletes but should be customised; keep the fluid deficit under 2% of body weight; take sodium when sweat rate is over 1.2 L/h, sweat is "salty," or exercise goes past 2 hours; do not drink more than you sweat.

How the math works

Total carbs = hours × the carbs per hour range (low end and high end).
Gels needed = total carbs ÷ carbs per gel, rounded up. Gels to carry adds 1 spare, as the guide says.
The schedule puts one gel at each interval while you are still going. You carry a little more than you take: the carry number rounds up and adds a spare.
Count any drink-mix carbs toward your total.
Body weight (optional) only changes the pre-ride or pre-run meal: 1 to 4 g of carbs per kg, 1 to 4 hours before exercise over 60 minutes, the same for riders and runners. It does not change carbs per hour during exercise, which the sources give in grams per hour (see Sources 3 and 9).
Rides under an hour: water is fine. Runs under 45 min: carbs are not needed.

Gut training tip (my approach, from the guide): your gut adapts. If 90 g/h upsets your stomach, start at 40 to 60 g/h on training rides and add about 10 g/h each week for 4 to 6 weeks. That schedule is my own, not from a study; the research above used about 2 weeks of repeated practice. Use the same gels and drinks you will race with, and never try anything new on race day.

More: How often should you take gels? · Free DIY Fuel Guide (PDF) · Shop the gel-making list

Sources

Everything below was opened and read for these numbers.

Thomas DT, Erdman KA, Burke LM. Nutrition and Athletic Performance (joint position statement of the Academy of Nutrition and Dietetics, Dietitians of Canada and the American College of Sports Medicine). Med Sci Sports Exerc 2016;48(3):543–568. Table 2: under 45 min "Not needed"; 45–75 min "Small amounts including mouth rinse"; 1–2.5 h "30–60 g/h"; 2.5+ h "Up to 90 g/h," with glucose:fructose mixtures. Before exercise over 60 min: 1–4 g/kg, 1–4 h before. Also fluid and sodium notes. doi.org/10.1249/MSS.0000000000000852
Burke LM, Hawley JA, Wong SH, Jeukendrup AE. Carbohydrates for training and competition. J Sports Sci 2011;29(S1):S17–27. "30–60 g/h is an appropriate target for sports of longer duration, events >2.5 h may benefit from higher intakes of up to 90 g/h." doi.org/10.1080/02640414.2011.585473
Jeukendrup AE. A step towards personalized sports nutrition: carbohydrate intake during exercise. Sports Med 2014;44(Suppl 1). Single carbohydrate "up to approximately 60 g/h" (2–3 h); about 90 g/h for ultra-endurance with multiple transportable carbohydrates; runner and cyclist advice "not different"; amounts adjusted downward at low intensity. On body weight: the during-exercise figures "are not corrected for body weight," and "there is no rationale for expressing carbohydrate recommendations for athletes per kilogram of BW." pmc.ncbi.nlm.nih.gov/articles/PMC4008807
Jeukendrup AE. Nutrition for endurance sports: marathon, triathlon, and road cycling. J Sports Sci 2011;29(S1):S91–S99. An earlier, more cautious table: 1–2 h up to 30 g/h; 2–3 h up to 60 g/h. doi.org/10.1080/02640414.2011.610348
de Oliveira EP, Burini RC, Jeukendrup A. Gastrointestinal complaints during exercise: prevalence, etiology, and nutritional recommendations. Sports Med 2014;44(Suppl 1):S79. pmc.ncbi.nlm.nih.gov/articles/PMC4008808
Peters HP, et al. Gastrointestinal symptoms in long-distance runners, cyclists, and triathletes: prevalence, medication, and etiology. Am J Gastroenterol 1999;94:1570–1581 (questionnaire of 606 well-trained athletes). Runners: lower-gut symptoms 71%, upper 36%. doi.org/10.1111/j.1572-0241.1999.01147.x
Martinez IG, Mika AS, Biesiekierski JR, Costa RJS. The effect of gut-training and feeding-challenge on markers of gastrointestinal status in response to endurance exercise: a systematic literature review. Sports Med 2023;53:1175. pmc.ncbi.nlm.nih.gov/articles/PMC10185635
Jeukendrup AE. Training the gut for athletes. Sports Med 2017;47(Suppl 1):101. "It is important to practice a race nutritional strategy in training." pmc.ncbi.nlm.nih.gov/articles/PMC5371619
Wallis GA, Podlogar T. Dietary carbohydrate and the endurance athlete: contemporary perspectives. Gatorade Sports Science Institute, Sports Science Exchange, October 2022. "Consuming carbohydrate quantities of 1 to 4 g·kg^-1 BM in the 1 to 4 h before exercise is recommended for exercise lasting > 60 min." gssiweb.org

Ride fluid and sodium numbers (and the 25 g per homemade gel) are my own estimates from the guide, not from these sources. Everything here is general guidance for healthy adults.