Running hydration: how much water should you carry?
Good running hydration starts with one question: how long will you be out? When it's hot, water isn't optional. But you don't need a vest for a park 5K. And you don't want one 500ml bottle 15 miles from home.
The rule is simple. Match what you carry to your time on your feet. Here's your running hydration at a glance.
| Time out | Roughly | What to carry |
|---|---|---|
| Under 30 min | 5K / easy | Pre-hydrate; grab a soft flask on hot days. Bottles & flasks → |
| 30–60 min | 10K | A handheld 500–600ml soft flask. Bottles & flasks → |
| 1–1.5 hrs | 10K → half | Hands-free: a belt or waist pack. Belts & packs → |
| 90 min+ | half → marathon | A hydration vest, flasks included. Hydration vests → |
Now let's take each in turn.
Under 30 minutes (~5K)
For a short, sharp run, skip the water. Drink well before you head out, and again when you're back. On a baking day, a pocket-size soft flask gives you a few sips. Soft flasks roll up as they empty, so nothing bounces.
Our pick: the Instinct Hydracell 600 Soft Flask (£16). It's light, compressible and easy to grip. Browse the full range of bottles and flasks.
30 to 60 minutes (~10K)
An hour in the heat means carrying water. One handheld soft flask of 500–600ml is plenty. Sip little and often, rather than gulping at halfway. Prefer nothing in your hand? A belt works well here too.
See the bottles and flasks collection for handhelds and straw-top options.
1 to 1.5 hours (10K to half marathon)
Past the hour mark, free up your hands. A belt or waist pack carries a flask, gels, keys and phone. It sits tight with zero bounce, so you forget it's there.
Our pick: the Instinct Running Reflex Belt (£40). It has six pockets and holds two 600ml soft flasks. On a budget, the Ronhill Marathon Waist Belt (£20) carries gels neatly. See all belts and packs.
90 minutes and beyond (half, marathon and ultra)
For the long stuff, a hydration vest is the answer. It carries a litre or more close to your body. The weight spreads across your shoulders, leaving room for layers and food. Most vests include soft flasks, so you're ready out of the box.
Our pick: the Salomon ADV Skin 5 (£125), our best-selling vest. It's a bounce-free fit, comfortable up to 60km. Want your first vest for less? Try the Inov8 Racepac 8 (£70). It holds two 500ml flasks plus a bladder. Explore all hydration vests.
Whatever you carry, add electrolytes
Here's what runners forget in the heat. When you sweat hard, plain water isn't enough. You lose salts as well as fluid. Topping up water alone can leave you flat.
Drop a single-serve drink mix into your flask. It replaces what you sweat out and steadies your energy. The STYRKR MIX90 drink mix (£3.75) is an easy, affordable start. See the full range of drink mixes and electrolytes.
Get your running hydration sorted
Not sure what suits you? Pop into the shop on Broad Street in Stamford. We'll help you find the right fit and fill. Shop the complete running hydration range online any time.
Prices and stock correct at time of writing (July 2026) and subject to change.