DIY Sports Drink Calculator

For most training scenarios, a 4–8% carbohydrate concentration is optimal — this is the isotonic range that balances energy delivery with gastric emptying speed. Below 4% (hypotonic) absorbs faster with less fuel; above 8% (hypertonic) provides more calories but can slow absorption and cause GI distress. For sessions under 60 minutes, 4–6% is usually sufficient; for longer efforts, 6–8% or a dual-carb (glucose + fructose) approach works best.

A good starting point is 400–600 mg of sodium per litre. Light trainers or those in cool conditions can use 200–400 mg/L, while heavy sweaters or athletes training in heat may benefit from 700–1000 mg/L. Sodium isn't just for taste — it drives fluid retention and maintains plasma volume, which is critical for endurance performance.

Osmolality measures the concentration of dissolved particles in your drink, expressed in mOsm/kg. Blood plasma sits around 280–300 mOsm/kg. Isotonic drinks match this range and absorb at a rate similar to plain water. Hypotonic drinks (< 270 mOsm/kg) absorb faster but deliver less fuel. Hypertonic drinks (> 300 mOsm/kg) provide more carbs and electrolytes but absorb more slowly — fine for fuelling but not for rapid rehydration.

The most effective approach for longer efforts is a 2:1 glucose-to-fructose mixture (e.g. dextrose + fructose or maltodextrin + fructose), which saturates different intestinal transporters and allows absorption of up to 90g of carbs per hour. For shorter sessions, simple sucrose (table sugar) works well and is cheap. Fruit juice provides a mix of natural sugars plus some potassium and flavour, making it a convenient base.

Start with your calculated volume of water, then add your measured sugar or carb source, a pinch of table salt (or sea salt) for sodium, and optionally a small amount of Lite Salt (potassium chloride) for potassium. Add fruit juice if desired for flavour. Stir until fully dissolved. This calculator gives you the exact gram and milligram amounts for each ingredient based on your bottle size and targets.

It depends on your goal. If your priority is fast rehydration (e.g. after a hard effort or in hot weather), a hypotonic drink absorbs most quickly. If you need both hydration and fuel during prolonged exercise, an isotonic drink is the best all-rounder. Hypertonic drinks are better used as fuel sources alongside plain water, rather than as a standalone hydration strategy.

Potassium is an intracellular electrolyte essential for muscle contraction and nerve function. While sodium is lost in far greater quantities through sweat, adding a small amount of potassium (from Lite Salt or No Salt products) can help maintain electrolyte balance and reduce cramping risk during long sessions. A typical target is 100–200 mg per litre.

Yes — fruit juice like orange, grape, or apple juice is a popular DIY base because it provides natural sugars, potassium, and flavour. However, undiluted juice is typically hypertonic, so it should be diluted with water and adjusted for your carb targets. This calculator accounts for your juice percentage so you don't over-add sugar on top of the juice's existing carbs.