Fuel and hydration planner

How the fuel planner works

Choose how long you'll be running and how much carbohydrate, fluid and sodium you want per hour. The planner splits those hourly amounts across the interval you pick, 20, 30 or 45 minutes, and lists what to take at each stop. It also totals everything and estimates how many gels you need to carry, based on the carbs per gel you enter. The last intake is timed before the finish rather than at it.

Where the starting numbers come from

• Carbohydrate. Sports-nutrition guidance, including the joint position of the American College of Sports Medicine and the Academy of Nutrition and Dietetics, suggests little or none for efforts under about 45 minutes, up to about 30 g per hour for 45 to 75 minutes, 30 to 60 g per hour for 1 to 2.5 hours, and up to 90 g per hour for longer efforts when it is a glucose and fructose mix and your stomach is trained for it.
• Fluid. A typical range is 400 to 800 ml (roughly 14 to 27 fl oz) per hour, tuned to your sweat rate. The general aim is to avoid losing more than about 2% of body weight.
• Sodium. Many runners do well with roughly 300 to 600 mg per hour, with heavy or salty sweaters needing more.

Finding your own sweat rate

Weigh yourself before and after a one-hour run, with no bathroom stop and nothing but known fluid intake:

Repeat in different weather, since heat and humidity change the answer.

Practical tips

• Most gels hold 20 to 25 g of carbs. Sports drinks commonly contain about 60 g per liter, so count the carbs in your drink toward the total.
• Rehearse your plan on long training runs. Fueling is a skill, and your stomach adapts with practice.
• Start fueling early, in the first 30 to 45 minutes, instead of waiting until you feel empty.

Limits

• These are general starting points, not medical or dietetic advice. Individual needs vary widely with body size, pace, heat and experience.
• Drinking more than you sweat can dangerously dilute blood sodium (hyponatremia). Don't force fluids beyond thirst and your measured sweat rate.
• If you have diabetes, kidney disease, high blood pressure or another condition affecting fluids, carbohydrate or sodium, talk to a doctor or sports dietitian first.

Planning the pace as well? Try the split strategy tool.