Fuel calculator
Your fuel plan, by the numbers.
Tell us what you're doing, how long, how hard and how hot. We'll turn it into a carbs-per-hour target, a gel count, a minute-by-minute schedule and the gel line that fits.
Calculator
Plug in your effort.
Duration does most of the work. Under an hour, one gel five minutes before you start is enough. Past an hour you fuel on the move, one gel every 20–30 minutes. Past two hours, aim for 60–90 g of carbs an hour, about three gels, plus electrolytes. Longer, harder or hotter than that and the Roctane line's extra sodium earns its place.
Recommended line
Schedule
Reminders
General guidance for education only, not medical or individual nutrition advice. Needs vary with body size, training history, health and conditions. Our gels complement a balanced diet, they don't replace one. Talk to a qualified sports dietitian or doctor before making big changes to how you fuel.
After the maths
How to use your result.
A number isn't a plan yet. Fuelling is a skill you train, the same way you train your legs, and these four habits turn the output above into something that holds up on race day.
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Train your gut, 6–8 weeks out
If you're new to fuelling, or the target is more than you take today, start gut training at least 6–8 weeks before race day. Build on your long sessions, week by week: 30 g of carbs an hour now, 40 g next week, 50 g the week after, until you reach the target. If you feel bloated, full or sick, hold that level for another week or step back one. Jumps of about 5 g an hour help you find your own limit. The gut adapts to what you ask of it: in one review of gut-training studies, two weeks of structured practice cut gut discomfort by an average of 47%.
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Practise at race pace
Take your planned gels at your planned interval on long sessions at goal pace, well before race week. Your gut behaves differently at race effort than on an easy run, so an interval that feels fine at a jog may not hold at pace. Then follow the golden rule: nothing new on race day. Same gel, same flavours, same timing you've already rehearsed.
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Pair every gel with water
Take each gel with a few sips of water. It helps your body absorb the carbs and eases the load on your gut. Start hydrated too, with 200–350 ml of fluid in the 1–2 hours before you head out, and over an hour aim for roughly 475–900 ml an hour with electrolytes, more if you sweat heavily. Liquid Energy Gel contains some water, but you still need to drink alongside it.
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Adjust for heat
Heat changes the maths. As your core temperature climbs, blood moves to the skin to cool you and away from the gut, so gels sit heavier and stomach trouble is more likely. On hot, humid days, a Mumbai long run in April, say, take smaller, more frequent doses, lean on Liquid Energy Gel, and switch to the Roctane line for up to 3x the sodium of the Original. If race day will be hot, train for it: 1–2 weeks of daily 90-minute sessions in the heat, or 2–4 weeks of 60-minute ones, builds most of the adaptation.
Questions
Calculator questions, answered.
What people ask once they've seen their number.
How many gels an hour can my stomach actually handle?
Most people absorb 30–60 g of carbs an hour from a single carb source without any training. Our gels blend maltodextrin and fructose, which use separate pathways in the gut, so 60–90 g an hour is realistic once you've trained for it. An Original or Roctane Energy Gel carries about 21 g of carbs and a Liquid Energy Gel 24 g, so three gels an hour lands in that band and four is the most the calculator will suggest. Above 90 g an hour is for well-trained guts only. How to train your gut.
Original or Roctane for my plan?
Both carry about the same carbs, so your gel count doesn't change. Roctane Energy Gel adds up to 3x the sodium and 3x the branched-chain amino acids of the Original, which is why the calculator recommends it when you go past three hours, push race intensity or fuel in the heat, when you're losing a lot of salt. Original Energy Gel is the everyday choice for steady training. Many people use Original through the week and keep Roctane for key workouts and race day. Roctane vs Original.
Do I need a gel for a 45-minute run or a gym session?
Not during it. Under 60 minutes, if you've eaten earlier in the day, your stored fuel covers the session. Top up instead: 20–30 g of carbs 5–15 minutes before you start, which is one Original Energy Gel, with a few sips of water. Save the bigger targets for sessions long or hard enough to need race-day practice. Fuel for strength training.
What if I can't face another gel halfway through?
Flavour fatigue is real past about four hours. Because carbs per packet are similar across our three gels, you can swap mid-race without redoing the maths: rotate flavours, move to Liquid Energy Gel for a thinner, lighter texture in the back half, or keep a caffeinated flavour for the last stretch. Keep the timing the same; only the packet changes. See the flavour and caffeine chart.
Plan done. Now stock it.
Order the line the calculator recommended, run the schedule on your next long session, and adjust from there.