Nutrition
Daily fluid from body weight
The core rule. Multiply weight in kilograms by the millilitres-per-kilogram guideline; 35 gives the familiar 2450 mL at 70 kg.
The Formula
V = w x r
The core rule. Multiply weight in kilograms by the millilitres-per-kilogram guideline; 35 gives the familiar 2450 mL at 70 kg.
| Symbol | Meaning | Unit | Notes |
|---|---|---|---|
| w | Body weight | kilograms | In kilograms. Pounds must be converted first, or the total is inflated by about 2.2 times. |
| r | Millilitres per kilogram per day | mL per kilogram per day | 35 mL/kg/day is the usual adult guideline; 30 to 40 covers lower and higher activity and climate. |
| V | Total daily fluid | millilitres | For 70 kg at 35 mL/kg this is 2450 mL, the total for a full day. |
What Each Symbol Means
wkilograms
Body weight
In kilograms. Pounds must be converted first, or the total is inflated by about 2.2 times.
rmL per kilogram per day
Millilitres per kilogram per day
35 mL/kg/day is the usual adult guideline; 30 to 40 covers lower and higher activity and climate.
Vmillilitres
Total daily fluid
For 70 kg at 35 mL/kg this is 2450 mL, the total for a full day.
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.