Running Nutrition Calculator
Fuelling shouldn't be the complicated part of a long run. Tell this calculator roughly how long you'll be out and how many carbs are in your gel, chew or drink, and it works out how much to carry and when to take it — as a time on the clock and, if you add your pace, a point on the course. It's free, ad-free, and there's nothing to sign up for.
Add your pace and the plan will show distance as well as time.
Most gels are 22–30g. Check the label on whatever you're using.
Fill in all three above to see your fuelling plan.
Carry this much
That's roughly of carbs across (about ).
How often
One about every , or roughly every . A rough schedule:
Heads up: for runs under an hour most people don't need to fuel at all - water is usually plenty.
A few honest caveats
- Start fuelling early - don't wait until you feel empty.
- Practise this in training, never first on race day. Guts need to be trained too.
- Carry water or sports drink alongside; carbs need fluid to absorb well.
- These are estimates to start from, not a prescription. Adjust to how you actually feel.
How it works
How does this calculator work
The calculator takes the carbs-per-hour you're aiming for and multiplies it by how long you'll be running. That gives the total carbohydrate you want to get through.
It then divides that total by the carbs in a single serving of your chosen fuel, and rounds up — so the number you carry always covers you rather than leaving you a gel short.
Finally it spaces those servings evenly across your run, nudged so you're not taking one on the start line or right at the finish. The result is a simple rhythm: one roughly every so many minutes. Add your average pace and it converts that rhythm into distance too, so you know you're due a gel at, say, the 8km mark rather than having to watch the clock.
Why it's useful
Why do you need to eat during runs?
Running out of fuel — the "bonk" or "hitting the wall" — is one of the most avoidable ways a good long run or race falls apart. Your body can only store so much glycogen, and once it's gone, pace and mood drop off a cliff. Taking in carbs steadily keeps the tank topped up.
The trouble is most people either guess, or copy whatever a friend does, and end up carrying too little or eating at random. This tool turns it into a plan you can actually rehearse: a clear number to pack and a clear cue for when to take each one. Practise that same plan on your long runs and race day becomes one less thing to think about.
And because it's just a calculator — no ads, no email wall, no upsell — you can use it the way you'd use a watch: open it, get your answer, get on with your run.
Frequently asked
Questions about eating during runs
How many carbs should I take per hour when running?
A common guide is around 30g per hour for easier or shorter efforts, about 60g per hour for most race-pace running, and up to 90g per hour for long efforts where you've trained your gut to handle it. Those higher intakes usually need a mix of glucose and fructose to absorb well.
Do I need gels on a 5k or a short run?
Usually not. For runs under about an hour you've already got enough stored glycogen, so water is generally all you need. Fuelling becomes worth planning once you're out beyond roughly 60 to 75 minutes.
How many gels do I need for a half marathon or marathon?
It depends on your finishing time and the carbs in each gel. As a rough example, a two-hour half at 60g per hour is about 120g of carbs — roughly five 25g gels. A four-hour marathon at the same rate is about 240g, or around ten gels. Pop your own numbers into the calculator above for a figure that fits you.
When should I take my first gel?
Start early, before you feel like you need it — often within the first 30 to 45 minutes. Topping up steadily keeps your energy even, whereas waiting until you feel empty means you're already behind.
Can I use chews, drink mix or real food instead of gels?
Yes. The calculator works on grams of carbohydrate, not the format. Read the carbs per serving off the label for chews, a scoop of drink mix, a banana or anything else, type that in, and the plan works the same way.
Is 90g of carbs per hour too much?
It's at the higher end and isn't for everyone. Intakes that high generally need fuel made from multiple carbohydrate types and a gut that's been trained over weeks of practice. Build up gradually rather than trying it for the first time on race day.
Do I still need water if I'm taking gels?
Yes. Carbohydrate needs fluid to absorb properly, and taking concentrated gels without enough water can upset your stomach. Carry water or a sports drink alongside your fuel.
Why does it round the number of servings up?
So you're never caught short on the course. Carrying one spare is a much smaller problem than running out with kilometres still to go.