Daily Water Intake by Body Weight Calculator

Hydration is fundamental to every body system — it regulates temperature, transports nutrients, supports joint cushioning, and affects cognitive performance. Yet most people either under-drink or lack a personalised target to aim for. The widely used half-your-body-weight-in-ounces rule provides a practical baseline that scales correctly with body size, then activity level adds additional ounces to replace sweat losses. A sedentary 120-pound person needs far less than a 220-pound athlete training twice daily. This calculator outputs your goal in ounces, liters, and cups so you can match it to whatever measurement your water bottle or tracking app uses. Enter your weight in pounds and select your activity level for a personalised daily target.

Base ounces = body weight (lbs) ÷ 2. This gives the minimum daily recommendation for a sedentary person at a neutral temperature. Activity level adds a fixed number of ounces on top: 0 oz for sedentary, 8 oz for light (1–3 days/week), 16 oz for moderate (3–5 days/week), 24 oz for active (6–7 days/week), and 32 oz for very active (twice-daily training). Total oz = base oz + activity oz. Liters = total oz × 0.02957 (the number of liters per fluid ounce). Cups = total oz ÷ 8, since one US cup equals 8 fluid ounces. The base figure is also displayed separately so you can see the activity contribution clearly.