About

How carbsperhour works

Q: How many carbs per hour should I consume on long endurance sessions?

Most trained athletes target 60 to 90 g/h on sessions over two hours, scaling up to 100 to 120 g/h on hard or long efforts if the gut is trained for it. The right number depends on duration, intensity, and how much GI training you've done — start at 60 g/h and add gradually.

Q: What is the right glucose to fructose ratio for endurance fueling?

Use roughly 2:1 glucose to fructose at moderate rates (60 to 90 g/h) and shift toward 1:0.8 above 90 g/h. The higher fructose share unlocks more usable carbs per hour by recruiting the GLUT5 transporter alongside SGLT1 (Hearris et al., 2022).

Q: Can I use table sugar as a sports drink ingredient?

Yes. Table sugar (sucrose) is 50% glucose and 50% fructose by mass, which is close to an ideal mix on its own. It's the cheapest DIY fueling option per gram of carbohydrate and dissolves easily. The downsides are sweetness at higher concentrations and a higher osmolarity than maltodextrin-based mixes.

Q: Is a homemade energy drink as effective as commercial gels?

For the same glucose to fructose ratio and total carb intake, a homemade mix delivers the same usable fuel as a branded gel or drink. Commercial products buy you convenience and consistency, not a unique chemistry. A DIY drink costs roughly a tenth as much per gram of carbohydrate.

Q: How much sodium should I add to my fueling plan?

A starting point is 300 to 700 mg of sodium per litre of fluid consumed, scaling up for hot conditions, long durations, or athletes who lose a lot of sodium in sweat. The calculator lets you set a per-session target; place all of it in one bottle so the others stay easy to drink.

Q: What concentration of carbohydrate should be in my bottle?

Isotonic sip bottles work best at 6 to 8% w/v. You can go to 14 to 18% for stronger mixes if your gut tolerates it. Above ~18% the drink becomes hypertonic and can slow gastric emptying — better placed in a concentrate flask sipped slowly rather than a main drinking bottle.

A carrier-aware DIY fueling calculator for endurance athletes. You tell it what ingredients you have on hand and which bottles you're riding with. It tells you what to put in each bottle, at what concentration, and where to place the sodium.

Why this tool exists

Most fueling calculators start with "tell me your target." carbsperhour starts with "tell me what you have." The DIY athlete already has a pantry — table sugar, maltodextrin, maybe fructose powder — and a bike with bidons. The tool's job is to respect that setup, not push a manufacturer's product page.

The painful part of the math isn't total grams per hour. It's the split — which gram of which ingredient goes in which bottle, what concentration that lands at, and whether you'll regret it in two hours. Most calculators stop at "you need 80 g/h." carbsperhour takes that number and produces a per-carrier recipe.

Free, no accounts, no subscription. The calculator is the product. The math runs in your browser — you can read the source and verify it yourself.

Methodology — glucose:fructose ratio

Glucose is absorbed via the intestinal transporter SGLT1, which saturates around 60 g/h. Fructose uses a separate transporter (GLUT5), so adding fructose alongside glucose unlocks an additional 30–50 g/h of usable carbohydrate without piling up unabsorbed sugar in the gut.

The right ratio depends on the rate:

At moderate rates (60–90 g/h): roughly 2 : 1 glucose to fructose.
Above ~90 g/h: shift toward 1 : 0.8 — almost equal — to take fuller advantage of the fructose pathway (Hearris 2022; Jeukendrup 2010).

The calculator's auto mode picks the ratio from the target g/h. You can override it manually if you have a preference or you already know your own tolerance.

Methodology — multi-ingredient solver

Given a target carb load and a desired ratio, the solver picks gram amounts of each selected ingredient. Each ingredient has known glucose and fructose percentages (see the ingredient reference), so the problem reduces to a small linear system.

For many input combinations there is more than one valid recipe — e.g. table sugar plus maltodextrin can hit a 1 : 0.8 ratio at several gram-pairs. The calculator picks the one that minimises your chosen criterion:

Closest-to-ratio — pure fidelity to the target G:F.
Cheapest — minimise total recipe cost in €.
Lowest osmolarity — gentler on the gut, useful at hot sessions.

Methodology — carrier split & concentration

Once the total grams are solved, the calculator splits them across your carriers (bottles, soft flasks) proportionally to their volume, respecting any physical capacity limits.

Concentration is reported as % w/v — grams of carbohydrate per 100 ml of fluid. Sip-bottle physiology:

≤ 8 % — hypotonic, absorbs fast, may not deliver enough carb.
8–14 % — sweet spot for sip bottles.
14–18 % — getting close to the isotonic ceiling; calculator emits a warning.
> 18 % — likely GI distress for sip use. Fine in a concentrate flask chased with plain water.

Sodium defaults to the largest carrier so the dose lands wherever you drink the most.

Methodology — cost & savings

Per-ingredient €/kg comes from typical German bulk retail prices (dm, Rossmann, Amazon.de, Decathlon, specialist sports-nutrition shops). Recipe cost is just Σ(grams × €/kg).

The "savings vs. gels" comparison uses a configurable reference price (default €2.20 per 25 g gel — typical Maurten / SiS retail). You can edit the reference numbers in the calculator; the override is stored in your browser's localStorage and never leaves your device.

Limitations & honest disclaimers

This is a calculator and an information tool. It is not medical advice and not a substitute for working with a sports nutritionist if you have one.

Ratio recommendations are population averages from the research literature. Individual GI tolerance varies by a lot. Experiment in training sessions, not on race day.

Some ingredient values are typical, not measured per batch — honey, agave, maple, and rice syrup compositions vary by origin and processing. The ingredient reference flags accuracy per-row.

Citations

Hearris MA, Pugh JN, Langan-Evans C, et al. 2022. "13C-glucose-fructose labelling reveals comparable exogenous CHO oxidation during exercise when consuming 120 g/h in fluid, gel, jelly chew or co-ingestion." Journal of Applied Physiology 132(6), 1394–1406.
Jeukendrup AE. 2010. "Carbohydrate and exercise performance: the role of multiple transportable carbohydrates." Current Opinion in Clinical Nutrition and Metabolic Care 13(4), 452–457.
Jentjens RL, Jeukendrup AE. 2005. "High rates of exogenous carbohydrate oxidation from a mixture of glucose and fructose ingested during prolonged cycling exercise." British Journal of Nutrition 93(4), 485–492.
Per-ingredient composition and osmolarity sources are listed inline on the ingredient reference page.

Frequently asked questions

How many carbs per hour should I consume on long endurance sessions?

Most trained athletes target 60–90 g/h on sessions over two hours, scaling up to 100–120 g/h on hard or long efforts if the gut is trained for it. The right number depends on duration, intensity, and how much GI training you've done — start at 60 g/h and add gradually.

What is the right glucose:fructose ratio for endurance fueling?

Use roughly 2:1 glucose:fructose at moderate rates (60–90 g/h) and shift toward 1:0.8 above 90 g/h. The higher fructose share unlocks more usable carbs per hour by recruiting the GLUT5 transporter alongside SGLT1 (Hearris et al., 2022).

Can I use table sugar as a sports drink ingredient?

Yes. Table sugar (sucrose) is 50% glucose / 50% fructose by mass, which is close to an ideal mix on its own. It's the cheapest DIY fueling option per gram of carbohydrate and dissolves easily. The downsides are sweetness at higher concentrations and a higher osmolarity than maltodextrin-based mixes.

What is maltodextrin and why is it used in sports nutrition?

Maltodextrin is a partly broken-down starch — a chain of glucose units. The body digests it into glucose nearly as fast as pure dextrose, but because it's a polymer it contributes less to the osmotic pressure of the drink. That means you can pack more carbs into the same volume of fluid without making it hypertonic, which is why almost every commercial sports drink uses it.

Is a homemade energy drink as effective as commercial gels?

For the same glucose:fructose ratio and total carb intake, a homemade mix delivers the same usable fuel as a branded gel or drink. Commercial products buy you convenience and consistency, not a unique chemistry. A DIY drink costs roughly a tenth as much per gram of carbohydrate.

How much sodium should I add to my fueling plan?

A starting point is 300–700 mg of sodium per litre of fluid consumed, scaling up for hot conditions, long durations, or athletes who lose a lot of sodium in sweat. The calculator lets you set a per-session target; place all of it in one bottle so the others stay easy to drink.

What concentration of carbohydrate should be in my bottle?

Isotonic sip bottles work best at 6–8% w/v. You can go to 14–18% for stronger mixes if your gut tolerates it. Above ~18% the drink becomes hypertonic and can slow gastric emptying — better placed in a concentrate flask sipped slowly rather than a main drinking bottle.

How do I split a fueling plan across multiple bottles?

The carbsperhour calculator does this automatically. You enter your carriers (e.g. 2× 750 ml bidons + 1× 150 ml soft flask), the total target carbs, and the ingredients you have; it returns per-bottle grams, resulting concentration in % w/v, and where to put the sodium so each bottle stays drinkable.