Nutrition Tools — Leafy Assistant, Race Calculator & Sweat Rate Test
Nutrition tools
Three free tools: a chatbot, a race fuelling calculator and a sweat rate test.
Fuelling advice usually stops one step short of being useful. “Sixty to ninety grams of carbohydrate an hour” is correct and almost impossible to act on the night before a race. These three tools exist to close that gap — to turn general guidance into your numbers, and your numbers into what actually goes in the vest.
Ask Leafy
Leafy answers questions about fuelling, hydration, recovery and which product suits a given session. Be specific — distance, expected time, conditions, and what has gone wrong before — and the answers get considerably better. Leafy is occasionally stubborn and still learning.
What Leafy is and is not. It is a conversational way into the same information published across this site. It is not a dietitian, it does not know your medical history, and it cannot see what you have bought. For anything involving a medical condition, medication, pregnancy or a diagnosed gut disorder, talk to a professional who can actually assess you.
Things worth asking
The questions that get the most useful answers are the specific ones.
- I’m running my first marathon in 4 hours 30. What should I carry?
- My stomach turns at about hour six of an ultra. What do I do?
- I don’t like gels. What are the alternatives?
- Which of your products has the most carbohydrate per serving?
- How do I fuel a long run that starts at 5am?
- I cramp badly in the heat. Is that a sodium problem?
- What should I eat in the 90 minutes before a race?
- Which products are vegan, and which contain honey?
The calculators
Both run on this site, both are free, and neither needs an account.
Before a race
Race nutrition calculator
Enter your event and expected finish time and it returns your carbohydrate, fluid and sodium targets per hour and for the whole race — then converts those grams into a specific list of products with quantities, a fuelling timeline, and the total cost. Works for anything from a half marathon to a hundred miler.
Build a race planOnce, in training
Sweat rate calculator
Weigh yourself before and after a 60 to 90 minute run and this gives you your sweat rate in litres per hour, how much fluid and sodium to replace, and which drink matches your losses. It accounts for the fact that sweating takes about 15 minutes to reach full rate, so a short test does not undercount you.
Measure your sweat rateWhich one to use, and when
| If you are asking | Use | Why |
|---|---|---|
| “How many gels do I need for my marathon?” | Race nutrition calculator | It works from published nutrition panels, so the answer is in grams and in actual products rather than a rule of thumb. |
| “How much should I drink?” | Sweat rate calculator first | Fluid and sodium advice is close to meaningless as an average. Measure yours once and every other number improves. |
| “Why does my stomach fail at hour six?” | Leafy | Diagnostic questions do not fit a form. This is a conversation. |
| “What is actually in this product?” | The nutrition data page | Every number for every product — carbohydrate, sodium, caffeine, allergens, ingredients and cost per serving — in one table. |
| “I am new to this and do not know where to start” | How to use Spring | The ground rules, before you start optimising anything. |
Common questions
What is Leafy?
Leafy is Spring Energy's nutrition chatbot. You can ask it about fuelling, hydration, recovery, which product suits a given session, and how to build a race plan. It is a conversational front end to the same information published across this site — it is not a dietitian, and it does not know anything about your medical history.
Which tool should I use?
Use the race nutrition calculator when you know how long an event will take and want to know what to carry, in grams and in actual products. Use the sweat rate calculator once, after a 60 to 90 minute test run, to turn your fluid and sodium numbers from an average into your own. Use Leafy for the questions that do not fit a form — what to do about a stomach that turns at hour six, how to fuel a double day, whether a product suits a specific session.
Is the nutrition advice here personalised?
Partly. The calculators use your body weight, your event duration, the conditions and, if you have measured it, your own sweat rate. What they cannot know is your medical history, your medication, your training background or how your gut has behaved in the past. Treat every number as a well-reasoned starting point to test in training, not a prescription.
Can Leafy tell me exactly how many gels I need?
It can, but the race nutrition calculator will do it more reliably, because it works from the published nutrition panel for every product rather than from a conversation. Ask Leafy the why questions and let the calculator do the arithmetic.
Are these tools free?
Yes. All three are free to use and require no account. They are on our own site rather than behind a login because the numbers are more useful to you than they are to us.
Do I need to buy Spring products to use the calculators?
No. The carbohydrate, fluid and sodium targets are general sports-nutrition figures and hold whatever brand you fuel with. The product plan is the last step, and it is there because converting grams per hour into actual packets is the part most people get wrong. If you fuel with something else, use the grams and ignore the list.
The calculators use published sports-nutrition ranges and our own verified product nutrition panels — see the complete nutrition data page. Nothing here is medical advice. Last reviewed: 14 August 2026.