Running fuel calculator

Runs under an hour do not need fuel. For longer runs, take a little carbohydrate often. Put in your run time to see how much, and in what form.

Your details

Fuel for a 2 hr run

30 to 60

grams of carbohydrate an hour

Total, starting after 30 minutes45 to 90 g
As 25 g gels2 to 4
Or jelly sweetsabout 5 g each

Little and often (every 20 to 30 minutes) sits better than a lot at once. Practise in training.

Diabetes or other medical conditions: ask your diabetes team about fuelling for long exercise.

The working

A two hour run

Between 1 and 2.5 hours the guidance is 30 to 60 g of carbohydrate an hour. Starting after 30 minutes, a 2 hour run needs 45 to 90 g: 2 to 4 gels of 25 g, or a handful of jelly sweets.

The bands

From the guidance

Duration	Carbohydrate
Under an hour	none needed
1 to 2.5 hours	30 to 60 g an hour
Over 2.5 hours	60 to 90 g an hour, mixed sugars

Train your gut

Practice pays

Try race day fuel on long training runs
Take small amounts every 20 to 30 minutes
Sip water with gels
Real food works too: bananas, dates, flapjack

Read with care

What this cannot tell you

Your gutSome people need to start lower and build up.
DiabetesTalk to your diabetes team about long exercise.
Pre race mealsThis covers fuel during the run only.

Questions

Common questions

When should I take my first gel?

Around 30 to 45 minutes in, then every 30 to 40 minutes.

How many gels for a marathon?

Often 5 to 8, depending on your time and the gel size.

Do I need gels for a 10K?

Usually not; under an hour, water is enough.

Sources

Last checked 21 October 2026. Spotted something wrong? Tell us and we will fix it.

Before you push on

New to exercise, or got a heart, lung or joint condition? Have a word with your GP or practice nurse first. Stop and get help if you feel chest pain, faintness or unusual breathlessness, and call 999 if it is severe.