Mixing & carrier calculator
DIY endurance fueling calculator
Pick ingredients, list carriers, set the session. The plan above shows what goes in each bottle.
Your plan
180 min · 90 g/h · 2:1 G:F
Up to datetotal carbs over your session
Recipe
Your prices
Gel reference
Numbers in your local currency (no symbol shown). Saved to this browser only.
Doesn't fit
0 g of mix can't be placed in your carriers (max 0 g across the lot).
Add another bottle or flask, or reduce your target carbs.
Session fluid
0.0 L total · 0.00 L/h
Average 0.0 g/100 ml across the session.
Doesn't change per-bottle warnings. The stomach feels each carrier's concentration as you drink it.
Take alongside
0 mg sodium, via salt caps or a separate electrolyte sip. Don't mix into the carb drink.
Show the math
Every number here follows a formula you can check. Nothing is a black box. The whole engine is open source.
- Total carbs
- target (g/h) × duration (min) ÷ 60
- Glucose:fructose ratio
- ~2:1 at 60–90 g/h, shifting toward ~1:0.8 above 90 g/h to push total absorption past the single-transporter ceiling (Hearris et al. 2022). What's the ratio?
- Per-ingredient grams
- the solver splits total carbs across your ingredients so the blend hits the target ratio, weighted by each one's composition (see the ingredient data).
- Concentration (g/100 ml)
- bottle carbs (g) ÷ bottle volume (ml) × 100. Above ~14 g/100 ml a drink turns hypertonic and can slow gastric emptying. Isotonic?
- Osmolality (mOsm/L)
- estimated per carrier from carb mass and molecular weight. Blood is ~290 mOsm/L; emptying slows past ~500. Osmolarity.
- Cost & savings
- Σ(grams × your €/kg) for the recipe; savings = gel-equivalent cost − recipe cost. Prices are editable and stored only in your browser.
Disclaimer: Educational tool, not medical advice. Self-experiment in training, not on race day. See the ingredient reference for source data.
Frequently asked
- How many carbs per hour should I aim for?
- Most amateurs sit in the 60 to 90 g/h band on sessions over two hours. 90 to 120 g/h is race-pace territory and needs a trained gut, so start around 60 and build up gradually.
- What glucose:fructose ratio should I use?
- Roughly 2:1 glucose to fructose at 60 to 90 g/h, shifting toward 1:0.8 above 90 g/h (Hearris 2022). The calculator's auto mode picks the ratio from your target rate, or you can set it yourself.
- Why does the calculator warn about concentration?
- Past your gut's comfortable ceiling, around 14 to 18 g per 100 ml for a trained gut, a drink turns hypertonic and leaves the stomach more slowly, which can cause GI distress. The calculator flags this per bottle so you can rebalance.
- Do I need maltodextrin, or is table sugar enough?
- Table sugar is already 50:50 glucose and fructose and works well on its own. Maltodextrin lets you pack more carbs into a bottle without it turning syrupy, because it adds less osmotic load per gram. The calculator solves for whichever you have.