Free tool · Nutrition

Carbs per hour calculator for training and racing

Short answer

The ACSM, Academy of Nutrition and Dietetics and Dietitians of Canada position statement advises no carbohydrate during exercise under 45 minutes, small amounts or a mouth rinse at 45–75 minutes, 30–60 g an hour for 1–2.5 hours, and up to 90 g an hour beyond 2.5–3 hours. A 2-hour session falls in the 30–60 g per hour band: 60–120 g in total.

Last reviewed 28 October 20262 published sourcesNot medical advice

Reps keeps track of this for you on iPhone, iPad and Apple Watch.

Get Reps free

Carbs per hour calculator

Carbohydrate during exercise by session length, from the ACSM, Academy of Nutrition and Dietetics and Dietitians of Canada position statement.

h
min

Enter how long your session or race will last.

Runs entirely in your browser. Nothing you type is saved or sent anywhere.

Carbohydrate during exercise (ACSM/AND/DC, 2016)
Session lengthCarbohydrate
Under 45 minutesNot needed
45–75 minutesSmall amounts, including mouth rinse
1–2.5 hours30–60 g per hour
Over 2.5–3 hoursUp to 90 g per hour
From the position statement's summary of carbohydrate guidelines for athletes (Thomas, Erdman & Burke, 2016).
Carbohydrate during exercise for well-trained athletes (Jeukendrup, 2014)
DurationAmountCarbohydrate type
30–75 minutesSmall amounts or mouth rinseSingle or multiple transportable
1–2 hoursUp to 30 g per hourSingle or multiple transportable
2–3 hoursUp to 60 g per hourSingle or multiple transportable
Over 2.5 hoursUp to 90 g per hourOnly multiple transportable
From Jeukendrup's Figure 1. He notes aspiring athletes may need to adjust these figures down (Jeukendrup, 2014).

Where the numbers come from

The joint ACSM, Academy of Nutrition and Dietetics and Dietitians of Canada position statement sets carbohydrate targets by how long you exercise: not needed under 45 minutes, small amounts including mouth rinse for 45–75 minutes, 30–60 g an hour for 1–2.5 hours (including stop-and-start sports), and up to 90 g an hour beyond 2.5–3 hours, where glucose and fructose mixtures help (Thomas, Erdman & Burke, 2016).

Jeukendrup's 2014 review gives a similar ladder for well-trained athletes: up to 30 g an hour for 1–2 hours, up to 60 g an hour for 2–3 hours and up to 90 g an hour beyond 2.5 hours, the last only from multiple transportable carbohydrates. A single carbohydrate source can be used at up to about 60 g an hour (Jeukendrup, 2014).

This calculator follows the position statement's bands; sessions between 75 minutes and 2.5 hours use the 30–60 g an hour row, and sessions of 60–75 minutes, which fall in both of its overlapping rows, use the 45–75 minute row.

Before and during the race

Fuelling during a race works best on top of full glycogen stores; plan those with the carb loading calculator. Fluid matters too: the water intake calculator estimates sweat losses from a training session.

Fuel and training, in one place

Reps logs what you eat next to your Apple Watch workouts and sleep, so race fuelling sits beside the sessions it is meant to power.

Download Reps on the App StoreNutrition in Reps

Free to download · iPhone, iPad and Apple Watch

Common questions

How many carbs per hour during a marathon?

It depends on your finish time. The ACSM position statement gives 30–60 g an hour for 1–2.5 hours of endurance exercise and up to 90 g an hour beyond 2.5–3 hours; over 4 hours, 90 g an hour adds up to 360 g.

Do I need carbs during a 1-hour workout?

Usually not much. For sustained high-intensity exercise of 45–75 minutes, the position statement suggests small amounts, including simply rinsing a sports drink around the mouth. Under 45 minutes, carbohydrate during exercise is not needed.

Why do high intakes need glucose and fructose?

Jeukendrup notes that a single type of carbohydrate can be used at up to about 60 g an hour. The 90 g an hour recommendation for long events relies on multiple transportable carbohydrates, such as glucose and fructose together. Glucose relies on one gut transporter that saturates at around 60 g an hour, while fructose uses a different one.

Sources

Figures on this page were checked against these publications on 28 October 2026.

  1. Thomas DT, Erdman KA, Burke LM. American College of Sports Medicine joint position statement: nutrition and athletic performance. Medicine & Science in Sports & Exercise. 2016;48(3):543–568. doi.org/10.1249/MSS.0000000000000852
  2. Jeukendrup A. A step towards personalized sports nutrition: carbohydrate intake during exercise. Sports Medicine. 2014;44(Suppl 1):S25–S33. doi.org/10.1007/s40279-014-0148-z

More nutrition tools

See every free tool →