Hydration 101: How Many mL per kg Do You Really Need?
Hydration is one of the most underestimated performance “supplements.” It impacts energy, focus, digestion, muscle function, training quality, and even appetite control. Yet, a large part of the population still doesn’t reach daily fluid intake recommendations.
In European surveys, only about 40.6% of men and 59.2% of women met their adequate intake target for fluids.
And the tricky part? Thirst is a late signal—often showing up once you’re already behind.
This guide gives you
- A simple mL/kg formula for daily hydration
- How much more you should drink during training
- What changes when you’re cutting weight
- 5 top products from our Drinks category to make hydration easier
Why most people are under-hydrated (even in winter)
Common reasons are boring but real:
- Busy days → you forget to drink
- Indoor heating / dry air → more water loss
- Caffeine → not “bad,” but it can reduce perceived thirst
- Dieting (“cutting”) → higher protein intake, more training, less food volume (less water from food)
- You wait for thirst → but mild dehydration can already impact how you feel and perform
Even mild dehydration (around 1–2% body water loss) can affect cognitive performance, and dehydration beyond ~2% body weight can degrade endurance performance.
The simple daily hydration formula (mL per kg)
A practical, easy-to-apply guideline used across multiple European dietary guideline sources is:
30–35 mL per kg of body weight per day
That’s total fluid intake (water + other drinks).
Examples (daily baseline)
- 60 kg → 1,800–2,100 mL/day
- 75 kg → 2,250–2,625 mL/day
- 90 kg → 2,700–3,150 mL/day
Quick reality check (EFSA reference)
EFSA’s adequate intake for total water is 2.0 L/day for women and 2.5 L/day for men (including water from food + fluids).
Practical tip: if you follow 30–35 mL/kg, you’ll usually land in the right zone for most active adults.
How much to drink during exercise (so you don’t crash)
Hydration during training isn’t “drink as much as possible.” The goal is to limit dehydration and avoid stomach sloshing.
A solid performance range:
0.4 to 0.8 L per hour during intense endurance activity.
What changes the number?
- Heat/humidity
- Sweat rate (some athletes lose a lot)
- Session duration
- Intensity
Electrolytes matter (especially if you sweat a lot)
For longer/hot sessions, drinks with sodium support hydration and fluid absorption. A commonly referenced range is ~500–700 mg sodium per liter.
Best electrolyte drink: 6D Sports Drink
If the session is >60 minutes and performance matters, 6D Sports Drink can be the better choice because it combines electrolytes + energy, is described as isotonic, and highlights a high salt concentration (900 mg sodium/L) plus 30 g carbs per 500 ml (so it supports fueling + hydration).
Best electrolyte
Help your hydratation
Simple field method (highly effective)
- Weigh yourself before training
- Weigh yourself after training
- If you lost >2% body weight, you likely under-drank and performance can suffer.
Hydration while “cutting”
Hydration often needs to be higher, not lower:
- Training volume often increases
- Protein intake increases
- Appetite and cravings are easier to manage when you’re hydrated
Rule: keep your 30–35 mL/kg baseline, then add what you need for training (often +400–800 mL/hour depending on sweat).
5 top hydration-friendly picks from our Drinks category
Pulled directly from our Boissons / Drinks page.
1) Bolero (sugar-free water flavour sachets)
Designed to help you drink regularly all day, with very low calories per liter—perfect for people who “hate plain water.”
2) Protein Water Drinks (Pat Nutrition)
A refreshing 500 ml protein drink (20 g protein) positioned for post-workout rehydration + protein in one.
3) Nutrend Carnitine Activity Drink with Caffeine (750 ml)
A large-format, sugar-free drink positioned to stay hydrated during training, with a convenient 750 ml bottle size for gym sessions.
4) Nocco BCAA Drinks (250 ml)
A sparkling, sugar-free option with BCAAs + caffeine. It’s not your “base hydration,” but it can be a useful pre-workout drink that still contributes fluid.
5) Bolero Energy
Powder to dilute in water, sugar-free, with caffeine/taurine/B-vitamins—useful when customers want a flavoured performance drink that also increases fluid intake.
💪 Coach note: caffeinated drinks can contribute to fluid intake, but for “real hydration” you still want most of your daily volume to be water + electrolyte-appropriate fluids when sweating heavily.
Best for your Water !
Helps you stay hydrated
Hydration checklist
- ✅ Daily target: 30–35 mL/kg
- ✅ During training: 0.4–0.8 L/hour
- ✅ Long/hot sessions: add electrolytes (sodium-focused)
- ✅ Avoid >2% body weight loss from dehydration
- ✅ Make it easy: flavour your water (Bolero), carry a big bottle (750 ml), and anchor habits (wake-up / meals / training)
FAQ
How many liters of water should I drink a day?
A simple baseline is 30–35 mL per kg body weight.
How do I know if I’m not hydrated enough?
Frequent headaches, low energy, poor training sessions, very dark urine, and strong late-day cravings are common signals.
Do I need electrolytes every time?
Not always. For short sessions (<1 hour) in cool conditions, water is often enough. For longer/hot sessions or heavy sweaters, electrolytes help.
Should I drink less water while cutting?
No: most people should maintain baseline hydration and adjust upward with training. Aggressive dehydration harms performance.
Sources
SCIENCE / GUIDELINES
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EFSA (2010) — Scientific Opinion on Dietary Reference Values for water
https://efsa.onlinelibrary.wiley.com/doi/10.2903/j.efsa.2010.1459 -
European Commission (Knowledge4Policy) — Food-Based Dietary Guidelines (Table 16)
https://knowledge4policy.ec.europa.eu/health-promotion-knowledge-gateway/food-based-dietary-guidelines-europe-table-16_en -
Ferreira-Pêgo et al. (2015) — Total fluid intake and its determinants
https://pmc.ncbi.nlm.nih.gov/articles/PMC4472938/ -
Riebl & Davy (2013) — The Hydration Equation (cognitive performance)
https://pmc.ncbi.nlm.nih.gov/articles/PMC4207053/ -
Mosler et al. (2020) — Fluid Replacement in Sports (position stand)
https://www.germanjournalsportsmedicine.com/fileadmin/content/archiv2020/Heft_7-8-9/DtschZSportmed_Position_Stand_Mosler_Fluid_Replacement_in_Sports_2020-7-8-9.pdf -
Cheuvront et al. (2003) — Fluid balance and endurance performance
https://pubmed.ncbi.nlm.nih.gov/12834575/
SPORT-NUTRITION.BE
7) Category page — Boissons
https://sport-nutrition.be/fr/shop/category/boissons-2228
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Bolero
https://sport-nutrition.be/fr/shop/bolero-16270 -
Protein Water Drinks (Pat Nutrition)
https://sport-nutrition.be/fr/shop/protein-water-drinks-17933 -
Nutrend Carnitine Activity Drink with Caffeine
https://sport-nutrition.be/fr/shop/nutrend-carnitine-activity-drink-with-caffeine-18753 -
Nocco BCAA Drinks 250 ml
https://sport-nutrition.be/fr/shop/nocco-bcaa-drinks-250-ml-16912 -
Bolero Energy
https://sport-nutrition.be/fr/shop/bolero-energy-18755