Skip to content
ENExplore Calculators

Water Requirement Calculator

Work out water requirement instantly with clear inputs, formula shown and shareable results.

About Water Requirement Calculator

Adds a weight-based baseline fluid requirement to the estimated sweat losses from training.

Formula

Fluid requirement

Total = weight (kg) x mL/kg/day + exercise hours x fluid loss per hour; 30 to 35 mL/kg/day is a common baseline

Worked example

With the default values below, Water Requirement Calculator returns Total daily fluid requirement of 2,910. Change any input above and every figure here is recalculated in your browser.

Inputs used

Weightaccepts 5–250 kg
70 kg
Baseline requirementaccepts 20–60 mL/kg/day
33 mL/kg/day
Hours of exerciseaccepts 0–8
1
Fluid loss per hour of exerciseaccepts 100–2,500 mL
600 mL

Results

Total daily fluid requirement
2,910 mL
Requirement
2.910 L
Baseline requirement
2,310 mL
Additional allowance for exercise
600 mL

Step by step

  1. 1Values used
  2. 2Fluid requirement
  3. 3Total daily fluid requirement= 2,910 mL
  4. 4Requirement= 2.910 L
  5. 5Baseline requirement= 2,310 mL
  6. 6Additional allowance for exercise= 600 mL

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • Educational estimate only. Not a substitute for professional clinical judgement, and must not be used to make treatment or dosing decisions.
  • This is an estimate for general information and not professional medical advice. See the full disclaimer for the limits that apply to this kind of calculator.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Educational estimate only. Not a substitute for professional clinical judgement, and must not be used to make treatment or dosing decisions.

Frequently Asked Questions

Does food count towards fluid intake?

Yes. Food typically supplies 20 to 30% of total water intake, which is why drinking targets are lower than total needs.

How can sweat rate be measured?

Weigh yourself before and after an hour of exercise: each kilogram lost is about one litre of sweat.

Related Calculators

Water Requirement Calculator | Calcrivo