How many gels you need for a half marathon depends on your finish time, the carbohydrate in each serving and whether you are also using a sports drink. A faster runner may need only one or two servings, while a runner on the course for two hours or more may need three or four.
The key is to plan your carbohydrate per hour, not simply count gel sachets. This guide gives you a practical starting point, with examples for different half-marathon finish times.
How many gels do you need for a half marathon?
For most runners, a sensible starting target is around 30–60g of carbohydrate per hour. If you are new to fuelling, start at the lower end and practise it on long runs. Experienced runners may tolerate more, but higher intakes should be built gradually rather than introduced on race day.
- 75-minute half marathon: around 40–75g of carbohydrate
- 90-minute half marathon: around 45–90g of carbohydrate
- 2-hour half marathon: around 60–120g of carbohydrate
- 2-hour 30-minute half marathon: around 75–150g of carbohydrate
Those totals include carbohydrate from gels, chews and sports drinks. If each gel contains around 30g of carbohydrate, a 90-minute race might call for one to three gel-equivalents depending on your target and what you take before or during the race.
Half-marathon gel plan by finish time
For a half marathon under 75 minutes
If you expect to finish in under 75 minutes, you may not need a large amount of carbohydrate during the race, particularly if you have eaten a familiar pre-race meal. Some runners still prefer one gel for confidence or a final push, but it should be tested during training.
- Eat a familiar carbohydrate-based meal or snack before the start.
- Take an optional gel 10–15 minutes before the race if you know it agrees with you.
- If taking a gel during the race, try one around 35–45 minutes.
- Take water according to the conditions and your own needs.
For a 75- to 90-minute half marathon
A runner finishing in this range may benefit from one or two gel servings during the race. Start early enough that you are fuelling before fatigue appears.
- Optional pre-race gel: 10–15 minutes before the start.
- First race gel: around 25–30 minutes.
- Second gel: around 55–65 minutes if needed.
If your gels contain different amounts of carbohydrate, adjust the number of servings. A larger serving may cover more of your hourly target, while a smaller gel may need to be combined with a drink or another serving.
For a 90-minute to 2-hour half marathon
For a longer half marathon, two or three gel servings is a useful starting point for many runners. The exact number depends on whether you are aiming closer to 30g or 60g of carbohydrate per hour.
- Take an optional top-up shortly before the start.
- Take your first gel at 20–30 minutes.
- Take another serving at around 55–65 minutes.
- Add a final serving at 85–95 minutes if your finish time and carbohydrate target require it.
Do not wait until the final kilometres to take all your fuel. Your body has to digest and use carbohydrate, so regular small servings are usually easier to manage than a large intake late in the race.
For a half marathon over 2 hours
If you will be running for more than two hours, plan your fuelling in the same way you would for a longer endurance event. Three or four gel-equivalents may be appropriate, especially if you are not getting carbohydrate from an on-course drink.
- Take your first serving within the first 25–30 minutes.
- Continue every 25–35 minutes.
- Carry a spare serving in case you miss an aid station or need to slow down.
- Consider using chews or a sports drink if several gels become difficult to tolerate.
Why gel size matters
Two gels do not necessarily provide the same amount of fuel. Check the nutrition panel and note the carbohydrate per serving. Your calculation is:
Carbohydrate per gel × number of gels = carbohydrate from gels.
Then add any carbohydrate from sports drinks or chews. For example, three 30g gels provide 90g of carbohydrate. If you also drink 20g per hour during a two-hour race, that adds another 40g, bringing the total to 130g.
This is why a plan based only on “one gel every 30 minutes” can be too little for one product and too much for another. Use the serving information on the packaging and choose a target you have practised.
Which gels should you use?
Choose a gel based on carbohydrate content, texture, flavour, caffeine and whether it needs water. The best option is the one you can take consistently without stomach problems.
For a higher-carbohydrate option, see the Precision Fuel & Hydration PF 90 Gel. If you want a smaller serving with caffeine, consider the Precision Fuel & Hydration PF 30 Caffeine Gel.
For SiS runners, compare the SiS BETA Fuel Gel and SiS GO Energy + Caffeine Gels. You can find more options in the Fuel collection.
Should you take a gel before a half marathon?
A pre-race gel can work well if you are starting early, have a long wait in the pen or prefer a small top-up instead of eating again. Take it 10–15 minutes before the start and drink water if the product instructions recommend it.
Do not use a pre-race gel to compensate for skipping breakfast or eating a meal that does not suit you. Keep your pre-race food familiar and practise the timing before race day.
Do you need caffeine gels for a half marathon?
Caffeine is optional. Some runners like one caffeine gel before the start or during the second half, while others prefer to keep every serving caffeine-free. If you use caffeine, test the product in training and count it alongside coffee, energy drinks and other sources.
A simple strategy is to use a regular gel early, then take one caffeine serving around halfway or with 30–40 minutes remaining. Do not try a new caffeine product for the first time during your race.
What should you drink with a gel?
Follow the instructions for the specific gel. Some products are designed to be taken with water, while isotonic gels may be formulated to be taken without a separate drink. Avoid taking a gel with a very concentrated sports drink unless the product guidance says it is suitable.
Take small sips at aid stations and adjust for the weather. More fluid is not automatically better, and your plan should reflect what you have tested on training runs.
Practise your half-marathon fuelling plan
Use a long run or race-pace session to test the exact products, timing and drink strategy you plan to use. Practise opening the packets while moving, carrying the right number of servings and taking them before you feel tired.
If your stomach feels uncomfortable, review the size and spacing of each serving, the concentration of your drinks and what you ate beforehand. Build up slowly rather than forcing a higher target. If you have a medical condition that affects eating or drinking during exercise, speak to a qualified healthcare professional or sports dietitian.
Half-marathon gel checklist
- Estimate your finish time.
- Choose a carbohydrate target per hour.
- Check the carbohydrate content of each gel.
- Include carbohydrate from drinks and chews.
- Plan your first serving for 20–30 minutes into the race.
- Decide whether you want a caffeine serving.
- Practise the full plan before race day.
- Carry one spare serving if you will be racing for more than 90 minutes.
For a broader race strategy, read our marathon fuelling plan. The distances are different, but the same principle applies: start early, count carbohydrate rather than sachets and use products you already trust.
