How much water do I need per day?

As a baseline, drinking 2.7 to 3.7 liters (90 to 125 oz) of fluids daily from water, beverages, and food is recommended. Active lifters require more to replace sweat losses.

Can mild dehydration affect strength workouts?

Yes, even a 2% drop in body water levels can cause up to a 10% decrease in strength performance and increase cardiovascular strain during exercise.

Hydration

The Science of Hydration: How Much Water Should You Drink Daily?

By Health Science Team • June 12, 2026 • 5 min read

Water constitutes approximately 60% of your total body mass. It is involved in regulating body temperature, lubricating joints, transporting nutrients, and clearing waste. To find your own personalized hydration target, check out our free Water Intake Calculator.

The Physiology of Hydration

Your body loses fluids constantly throughout the day through breathing, sweating, urine, and metabolic functions. If these fluids are not replaced, your physical and cognitive performance will suffer. Studies show that a dehydration level of just 2% of body weight can impair muscle endurance, increase fatigue, and reduce coordination.

How to Calculate Your Fluid Needs

Your daily water needs depend on your weight, activity levels, and environment:

Base Intake: A common rule of thumb is to drink 0.5 to 1.0 ounces of water per pound of body weight (or about 30 to 35 ml per kg).
Activity Adjustment: Add 12 to 20 ounces (350 to 600 ml) of water for every 30 minutes of intense training to replace sweat loss.
Climate Factor: Hot or humid conditions increase sweat rates, requiring an additional 16 to 32 ounces (500 to 1000 ml) of fluids.

Hydration Indicators

The easiest way to track hydration is by monitoring the color of your urine. A pale straw or clear color indicates good hydration, while dark yellow or amber urine suggests you need to drink more fluids immediately.

Summary

Keep your hydration levels high to support your physical training. Calculate daily maintenance calories using our main TDEE Calculator, track protein using our Protein Calculator, check macros using our Macro Calculator, and estimate body fat levels with our Body Fat Calculator.