DIY Sports Drink Calculator

Tonicity measures the concentration of dissolved particles in a liquid relative to blood plasma (~280–295 mOsm/kg). A hypotonic drink (below ~270 mOsm/kg) absorbs fastest, isotonic (~270–330 mOsm/kg) absorbs at a moderate rate, and hypertonic (above ~330 mOsm/kg) can draw fluid into the gut and cause GI distress. For high-intensity exercise, keeping your drink isotonic or slightly hypotonic generally works best.

A 2:1 ratio of glucose-based carbs (like maltodextrin) to fructose is widely recommended for endurance sports, as the two sugars use different intestinal transporters — allowing up to 90g of carbs per hour to be absorbed. A 70/30 split (maltodextrin/fructose) is a popular starting point that balances absorption and palatability.

Sodium needs vary widely based on sweat rate, sweat sodium concentration, and environment. Most athletes do well with 300–700mg per hour. If you're training in heat, are a heavy or salty sweater, or exercising for more than 2 hours, consider targeting 700–1000mg/hr. Start conservatively and adjust based on how you feel.

DE stands for Dextrose Equivalent — it measures how much the maltodextrin has been broken down from its original starch form. A higher DE means shorter chains, more sweetness, and higher osmotic pressure. Most common maltodextrin powders have a DE of 15–20. Check the product label or ask the supplier; it significantly affects your drink's tonicity calculation.

Sodium citrate provides sodium without the harsh chloride taste of table salt, making the drink more palatable. It also acts as a mild buffer, which may reduce acid buildup in muscles during intense efforts. The sodium content in sodium citrate is roughly 27% by weight, so 1g of sodium citrate provides about 270mg of sodium.

Yes — the same formula works for any endurance activity. However, runners often need to be more conservative with carb concentration because running's vertical movement increases GI stress compared to cycling. Starting with a more hypotonic mix (lower carb concentration) is wise for runners, especially during races.

DIY sports drinks give you full control over ingredients and ratios, often at a fraction of the cost. Commercial drinks use simple sugars with added flavoring, coloring, and preservatives. By using maltodextrin, you get more carbs at a lower osmolarity than glucose or sucrose-based drinks, meaning you can fuel more aggressively without spiking GI distress.

Citric acid adds a light, tart lemon flavor that makes the drink more palatable during long efforts — especially important when sweet flavors become nauseating. It has negligible caloric value and a minor effect on tonicity at typical doses (around 1g per bottle). It's entirely optional and can be skipped if you prefer a neutral-tasting drink.