Nutrition
Adjusting for losses and gains
The baseline is only a starting point. Add losses from heat, exercise and altitude, then subtract what food and other drinks already contribute.
The Formula
target = base + sweat loss - fluid from food
The baseline is only a starting point. Add losses from heat, exercise and altitude, then subtract what food and other drinks already contribute.
| Symbol | Meaning | Unit | Notes |
|---|---|---|---|
| base | Baseline from body weight | millilitres | 35 mL/kg for a 70 kg adult gives 2450 mL. |
| S | Added loss from heat and exercise | millilitres | Sweat rates of 500 to 1500 mL per hour are common in hard training. |
| F | Fluid supplied by food and other drinks | millilitres | Often a large share of the total, so the plain-water target sits below the headline figure. |
What Each Symbol Means
basemillilitres
Baseline from body weight
35 mL/kg for a 70 kg adult gives 2450 mL.
Smillilitres
Added loss from heat and exercise
Sweat rates of 500 to 1500 mL per hour are common in hard training.
Fmillilitres
Fluid supplied by food and other drinks
Often a large share of the total, so the plain-water target sits below the headline figure.
See It Worked With Real Numbers
A formula on its own does not tell you which number goes where. The how to calculate water intake page applies this equation to a concrete case, shows every intermediate step, and names the mistakes that produce a wrong answer even when the algebra is right.
Where This Formula Appears
This equation is the working core of How To Calculate Water Intake, filed under Health. Every number the guide produces comes from substituting into this one line.