Quick answer
Running fueling should scale by distance: 5K and 10K races mostly need pre-race carbohydrate timing, half marathons usually need 30-45g carbs/hour, and marathons require a practiced 45-75g/hour plan with hydration and sodium.
3 key facts
- Race duration, not distance alone, determines whether in-race carbohydrates are needed.
- Half marathon and marathon fueling works best when gels are scheduled by time instead of taken only when fatigue appears.
- Mavr converts finish-time goals into personalized carb, gel, hydration, and sodium targets.
Most runners either underfuel shorter races or overcomplicate longer ones. This guide gives you straightforward targets by distance so your energy stays stable from start to finish.
Carb targets by race distance
5K / 10K
Typical Duration20–60 min
Carb TargetNo in-race carbs needed for most runners
Half Marathon
Typical Duration75–150 min
Carb Target30–45g carbs/hour
Marathon
Typical Duration2–5 hours
Carb Target45–75g carbs/hour
| Distance | Typical Duration | Carb Target |
|---|---|---|
| 5K / 10K | 20–60 min | No in-race carbs needed for most runners |
| Half Marathon | 75–150 min | 30–45g carbs/hour |
| Marathon | 2–5 hours | 45–75g carbs/hour |
Runners who have practiced race fuel in long runs can often go higher in a marathon, up to 60–90g carbs/hour. For fluid, sipping to thirst is enough for most 5K and 10K races. In a half marathon, many runners drink about 400–700 ml per hour, and in a marathon about 500–800 ml per hour. Aim for the top of the range in heat and the bottom in cool weather.
Simple race-day timeline
- Final 24 hours: avoid new high-fiber or high-fat foods.
- 2–3 hours pre-race: 1–2g carbs/kg from familiar foods.
- 10–15 minutes pre-start: 20–25g quick carbs.
- Half marathon+: first gel around 30–40 minutes, then every 30–40 minutes.
- Hydrate to thirst and include sodium in warm conditions.
- Fuel by the clock, not by feel: set your gel times before the start.
- Carry backup fuel in case you miss an aid station or it runs out.
Common race fueling mistakes
- Skipping breakfast because of race nerves.
- Trying a new caffeine dose on race day instead of one you tested in training.
- Copying another runner's plan without matching your pace, duration, and sweat rate.
Frequently asked questions
How should fueling change from 5K to marathon?
Short races usually need a practiced pre-race meal and fluids, while half marathon and marathon racing need planned carbohydrate during the event. The longer the race, the more timing, gut practice, sodium, and hydration matter.
Do I need gels for a 5K or 10K?
Most runners do not need gels during a 5K or 10K. A familiar pre-race meal or snack is usually enough unless the event is unusually long for your pace or conditions are hot.
What is the biggest marathon fueling mistake?
Starting fuel too late is the most common mistake. Marathon runners should practice taking carbohydrate early and consistently instead of waiting until fatigue appears.
Do I need electrolytes for a half marathon?
Many runners benefit from some sodium in a half marathon, especially in heat or if sweat losses are high. A sports drink on the course or an electrolyte tab in your bottle is an easy way to get it.
Can I race a 5K or 10K fasted?
You can, but most runners perform better with a familiar pre-race meal or snack that supports hard efforts. If there is no time for a meal, the 20–25g quick-carb snack 10–15 minutes before the start still helps.
Can Mavr build fueling by race distance?
Yes. Mavr can adjust pre-race, during-race, hydration, sodium, and recovery targets based on race distance, expected duration, and workout history.
General guidance for healthy adults, not medical advice. Talk to a doctor or registered dietitian if you have a health condition, take medicines or have special dietary needs. Caffeine advice is for healthy adults only. EFSA's safe limit is 200 mg in one dose and 400 mg in a day.
